diff --git a/CSES/Tree Algorithms/Company Queries I.cpp b/CSES/Tree Algorithms/Company Queries I.cpp
new file mode 100644
index 0000000..c8b3c7b
--- /dev/null
+++ b/CSES/Tree Algorithms/Company Queries I.cpp	
@@ -0,0 +1,78 @@
+/*
+ * Problem Name : Company Queries I
+ * Problem Link : https://cses.fi/problemset/task/1687/
+ * Video solution link : https://youtu.be/H8h8XazNOV4
+ * Write here if video solution doesn't exist : icodencode@gmail.com
+ * Channel name & link : CodeNCode (https://www.youtube.com/@codencode)
+ */
+
+#include<bits/stdc++.h>
+#define REP(i,n) for (int i = 1; i <= n; i++)
+#define mod 1000000007
+#define pb push_back
+#define ff first
+#define ss second
+#define ii pair<int,int>
+#define vi vector<int>
+#define vii vector<ii>
+#define lli long long int
+#define INF 1000000000
+#define endl '\n'
+const double PI = 3.141592653589793238460;
+typedef std::complex<double> Complex;
+typedef std::valarray<Complex> CArray;
+using namespace std;
+ 
+const int maxN = 21;
+vi ar[200001];
+int dp[200001][maxN];
+int n;
+ 
+void preprocess()
+{
+	for(int i=1;i<maxN;i++)
+	{
+		for(int j=1;j<=n;j++)
+		{
+			int par = dp[j][i-1];
+			
+			if(par == -1) continue;
+			else
+			dp[j][i] = dp[par][i-1];
+		}
+	}
+}
+ 
+int getKthPar(int node , int k)
+{
+	int i = 0;
+	
+	while(i < maxN)
+	{
+		if( (k & (1 << i)) && (dp[node][i] != -1))
+		node = dp[node][i] , k -= (1 << i);
+		
+		i++;
+	}
+	
+	if(k > 0) node = -1;
+	return node;
+}
+ 
+int main()
+{
+	int q , a , k;
+	cin>>n>>q;
+	
+	memset(dp , -1 , sizeof dp);
+	for(int i=2;i<=n;i++) cin>>a , dp[i][0] = a;
+	
+	preprocess();
+	
+	while(q--)
+	{
+		cin>>a>>k;
+		
+		cout<<getKthPar(a , k)<<endl;
+	}
+}
diff --git a/CSES/Tree Algorithms/Distinct Colors.cpp b/CSES/Tree Algorithms/Distinct Colors.cpp
new file mode 100644
index 0000000..4bd40f2
--- /dev/null
+++ b/CSES/Tree Algorithms/Distinct Colors.cpp	
@@ -0,0 +1,63 @@
+#include<bits/stdc++.h>
+#define REP(i,n) for (int i = 1; i <= n; i++)
+#define mod 1000000007
+#define pb push_back
+#define ff first
+#define ss second
+#define ii pair<int,int>
+#define vi vector<int>
+#define vii vector<ii>
+#define lli long long int
+#define INF 1000000000
+#define endl '\n'
+const double PI = 3.141592653589793238460;
+typedef std::complex<double> Complex;
+typedef std::valarray<Complex> CArray;
+using namespace std;
+ 
+int c[200002];
+int res[200001];
+vi ar[200002];
+set<int> *st[200001];
+ 
+void dfs(int node, int par)
+{
+	int mx = 0;
+	int mxNode = -1;
+	
+	for(int child : ar[node])
+	if(child != par)
+	{
+		dfs(child , node);
+		if( st[child]->size() > mx )
+		mx = st[child]->size() , mxNode = child;
+	}
+	
+	if(mxNode == -1) st[node] = new set<int>();
+	else			 st[node] = st[mxNode];
+	
+	st[node] -> insert(c[node]);
+	
+	for(int child : ar[node])
+	if(child != par && child != mxNode)
+	{
+		for(int color : *st[child])
+		st[node]->insert(color);
+	}
+	
+	res[node] = st[node] -> size();
+}
+ 
+int main()
+{
+	int n , a , b;
+	cin>>n;
+	REP(i , n) cin>>c[i];
+	
+	REP(i , n-1) cin>>a>>b , ar[a].pb(b) , ar[b].pb(a);
+	
+	dfs(1 , -1);
+	
+	REP(i , n) cout<<res[i]<<" ";
+}
+ 
diff --git a/CSES/Tree Algorithms/Finding a Centroid.cpp b/CSES/Tree Algorithms/Finding a Centroid.cpp
new file mode 100644
index 0000000..b9daaa1
--- /dev/null
+++ b/CSES/Tree Algorithms/Finding a Centroid.cpp	
@@ -0,0 +1,52 @@
+#include<bits/stdc++.h>
+#define REP(i,n) for (int i = 1; i <= n; i++)
+#define mod 1000000007
+#define pb push_back
+#define ff first
+#define ss second
+#define ii pair<int,int>
+#define vi vector<int>
+#define vii vector<ii>
+#define lli long long int
+#define INF 1000000000
+#define endl '\n'
+const double PI = 3.141592653589793238460;
+typedef std::complex<double> Complex;
+typedef std::valarray<Complex> CArray;
+using namespace std;
+ 
+int sub[200001];
+int n;
+vi ar[200001];
+ 
+void subSize(int node ,int par)
+{
+	sub[node] = 1;
+	
+	for(int child : ar[node])
+	if(child != par)
+	{
+		subSize(child , node);
+		sub[node] += sub[child];
+	}
+}
+ 
+int centroid(int node , int par)
+{
+	for(int child : ar[node])
+	if(child != par && sub[child] > n/2) return centroid(child , node);
+	
+	return node;
+}
+ 
+int main()
+{
+	int a , b;
+	cin>>n;
+	
+	REP(i , n-1) cin>>a>>b , ar[a].pb(b) , ar[b].pb(a);
+	
+	subSize(1 , -1);
+	cout<<centroid(1 , -1);
+}
+ 
diff --git a/CSES/Tree Algorithms/Subtree Queries.cpp b/CSES/Tree Algorithms/Subtree Queries.cpp
new file mode 100644
index 0000000..c5cd09b
--- /dev/null
+++ b/CSES/Tree Algorithms/Subtree Queries.cpp	
@@ -0,0 +1,113 @@
+#include<bits/stdc++.h>
+#define REP(i,n) for (int i = 1; i <= n; i++)
+#define mod 1000000007
+#define pb push_back
+#define ff first
+#define ss second
+#define ii pair<int,int>
+#define vi vector<int>
+#define vii vector<ii>
+#define lli long long int
+#define INF 1000000000
+#define endl '\n'
+const double PI = 3.141592653589793238460;
+typedef std::complex<double> Complex;
+typedef std::valarray<Complex> CArray;
+using namespace std;
+ 
+const int N = 200001;
+vi tree[N];
+ 
+lli ar[N];
+lli temp[N];
+ 
+lli st[2*N];
+ 
+lli sub[N];
+lli in[N];
+int _timer = 0;
+ 
+void dfs(int node, int par)
+{
+	sub[node] = 1;
+	in[node] = ++_timer;
+	ar[in[node]] = temp[node];
+	
+	for(int child : tree[node])
+	if(child != par)
+	dfs(child , node) , sub[node] += sub[child];
+}
+ 
+void build(int si , int ss , int se)
+{
+	
+	if(ss == se){
+		st[si] = ar[ss];
+		return;
+	}
+	
+	int mid = (ss + se) >> 1;
+	build(2*si , ss , mid);
+	build(2*si + 1 , mid+1 , se);
+	
+	st[si] = st[2*si] + st[2*si + 1];
+}
+ 
+void update(int si , int ss , int se , int qi , lli dx)
+{
+	if(ss > qi || se < qi) return;
+	
+	if(ss == se)
+	{
+		st[si] += dx;
+		return;
+	}
+	
+	int mid = (ss + se) >> 1;
+	update(2*si , ss , mid , qi , dx);
+	update(2*si + 1 , mid+1 , se , qi , dx);
+	
+	st[si] = st[2*si] + st[2*si + 1];
+}
+ 
+lli getSum(int si , int ss , int se , int qs , int qe)
+{
+	if(ss > qe || se < qs) return 0;
+	
+	if(ss >= qs && se <= qe)
+	return st[si];
+	
+	int mid = (ss + se) >> 1;
+	lli L = getSum(2*si , ss , mid , qs , qe);
+	lli R = getSum(2*si + 1 , mid+1 , se , qs , qe);
+	
+	return L + R;
+}
+ 
+int main()
+{
+	int n , q , a , b , code;
+	cin>>n>>q;
+	
+	REP(i , n) cin>>temp[i];
+	REP(i , n-1) cin>>a>>b , tree[a].pb(b) , tree[b].pb(a);
+	
+	dfs(1 , -1);
+	build(1 , 1 , n);
+	
+	while(q--)
+	{
+		cin>>code;
+		
+		if(code == 1) {
+			cin>>a>>b;
+			update(1 , 1 , n , in[a] , b - ar[in[a]]);
+			ar[in[a]] = b;
+		}
+		else{
+			cin>>a;
+			cout<<getSum(1 , 1 , n , in[a] , in[a] + sub[a] - 1)<<endl;
+		}
+	}
+}
+ 
diff --git a/CSES/Tree Algorithms/Tree Diameter.cpp b/CSES/Tree Algorithms/Tree Diameter.cpp
new file mode 100644
index 0000000..11d432c
--- /dev/null
+++ b/CSES/Tree Algorithms/Tree Diameter.cpp	
@@ -0,0 +1,55 @@
+#include<bits/stdc++.h>
+#define REP(i,n) for (int i = 1; i <= n; i++)
+#define mod 1000000007
+#define pb push_back
+#define ff first
+#define ss second
+#define ii pair<int,int>
+#define vi vector<int>
+#define vii vector<ii>
+#define lli long long int
+#define INF 1000000000
+#define endl '\n'
+const double PI = 3.141592653589793238460;
+typedef std::complex<double> Complex;
+typedef std::valarray<Complex> CArray;
+using namespace std;
+ 
+vi ar[200001];
+int f[200001];
+int g[200001];
+int d;
+ 
+void dfs(int node ,int par)
+{
+	vi childList;
+	
+	for(int child : ar[node])
+	if(child != par)
+	{
+		dfs(child , node);
+		f[node] = max(f[node] , f[child] + 1);
+		childList.pb(f[child]);
+	}
+	
+	d = max(d , f[node]);
+	
+	sort(childList.begin() , childList.end());
+	if(childList.size() >= 2)
+	{
+		g[node] = 2 + childList[childList.size()-1] + childList[childList.size()-2];
+		d = max(d , g[node]);
+	}
+}
+ 
+int main()
+{
+	int n , a , b;
+	cin>>n;
+	REP(i , n-1) cin>>a>>b , ar[a].pb(b) , ar[b].pb(a);
+	
+	dfs(1 , -1);
+	
+	cout<<d;
+}
+ 
diff --git a/CSES/Tree Algorithms/Tree Distances II.cpp b/CSES/Tree Algorithms/Tree Distances II.cpp
new file mode 100644
index 0000000..0b0fad7
--- /dev/null
+++ b/CSES/Tree Algorithms/Tree Distances II.cpp	
@@ -0,0 +1,61 @@
+#include<bits/stdc++.h>
+#define REP(i,n) for (int i = 1; i <= n; i++)
+#define mod 1000000007
+#define pb push_back
+#define ff first
+#define ss second
+#define ii pair<int,int>
+#define vi vector<int>
+#define vii vector<ii>
+#define lli long long int
+#define INF 1000000000
+#define endl '\n'
+const double PI = 3.141592653589793238460;
+typedef std::complex<double> Complex;
+typedef std::valarray<Complex> CArray;
+using namespace std;
+ 
+vi ar[200001];
+lli res[200001];
+int subSize[200001];
+lli subDist[200001];
+int n;
+ 
+void dfs1(int node , int par)
+{
+	subSize[node] = 1;
+	
+	for(int child : ar[node])
+	if(child != par)
+	{
+		dfs1(child , node);
+		subSize[node] += subSize[child];
+		
+		subDist[node] += subSize[child] + subDist[child];
+	}
+}
+ 
+void dfs(int node , int par)
+{
+	res[node] = res[par] - subSize[node] - subDist[node] + n - subSize[node] + subDist[node];
+	
+	for(int child : ar[node])
+	if(child != par)
+	dfs(child , node);
+}
+ 
+int main()
+{
+	int a , b;
+	cin>>n;
+	REP(i , n-1) cin>>a>>b , ar[a].pb(b) , ar[b].pb(a);
+	
+	dfs1(1 , -1);
+	res[1] = subDist[1];
+	
+	for(int child : ar[1])
+	dfs(child , 1);
+	
+	REP(i , n) cout<<res[i]<<" ";
+}
+ 
diff --git a/Codeforces/Editorials/Greedy Algorithms/Creating a Schedule.cpp b/Codeforces/Editorials/Greedy Algorithms/Creating a Schedule.cpp
new file mode 100644
index 0000000..1ecf010
--- /dev/null
+++ b/Codeforces/Editorials/Greedy Algorithms/Creating a Schedule.cpp	
@@ -0,0 +1,72 @@
+/*
+ * Problem Name : D. Creating a Schedule
+ * Problem Link : https://codeforces.com/contest/2111/problem/D
+ * Video solution link : https://youtu.be/TKrhq5hy6IA
+ * Write here if video solution doesn't exist : icodencode@gmail.com
+ * Channel name & link : CodeNCode (https://www.youtube.com/@codencode)
+ */
+
+#include <iostream>
+#include <vector>
+#include <algorithm>
+
+using namespace std;
+
+// Extracts floor number from classroom number
+int get_floor(int classroom) {
+    return classroom / 100;
+}
+
+bool comp(int a, int b) {
+	return get_floor(a) < get_floor(b);
+}
+int main() {
+    int t;
+    cin >> t;
+
+    while (t--) {
+        int n, m;
+        cin >> n >> m;
+
+        vector<int> classrooms(m);
+        for (int i = 0; i < m; ++i)
+            cin >> classrooms[i];
+
+        sort(classrooms.begin(), classrooms.end(), comp);
+
+        vector<vector<int>> schedule(n, vector<int>(6));
+        int left = 0, right = m-1;
+
+        for (int i = 1; i < n; i+=2) {
+        	schedule[i  ][0] = classrooms[left++];
+            	schedule[i-1][0] = classrooms[right--];
+        }
+        
+        for(int k=1; k<6; k++) {
+        	for(int i=1; i<n; i+=2) {
+        		schedule[i  ][k] = schedule[i-1][k-1];
+            		schedule[i-1][k] = schedule[i  ][k-1];
+		}
+	}
+		
+	if(n & 1) {
+		for(int k=0; k<6; k++) {
+			if(k & 1)
+			schedule[n-1][k] = classrooms[left];
+			else
+			schedule[n-1][k] = classrooms[right];
+		}
+	}
+
+        for (int i = 0; i < n; ++i) {
+        	for (int k = 0; k < 6; ++k) {
+        		cout << schedule[i][k] << " ";
+	        }
+            cout << '\n';
+        }
+        
+    }
+
+    return 0;
+}
+
diff --git a/Codeforces/Editorials/Greedy Algorithms/Make It Good.cpp b/Codeforces/Editorials/Greedy Algorithms/Make It Good.cpp
new file mode 100644
index 0000000..0fc54c6
--- /dev/null
+++ b/Codeforces/Editorials/Greedy Algorithms/Make It Good.cpp	
@@ -0,0 +1,86 @@
+/*
+ * Problem Name : C. Make It Good
+ * Problem Link : https://codeforces.com/contest/1385/problem/C
+ * Video solution link : https://youtu.be/qmUGfEYLYew
+ * Write here if video solution doesn't exist : icodencode@gmail.com
+ * Channel name & link : CodeNCode (https://www.youtube.com/@codencode)
+ */
+
+
+#include<bits/stdc++.h>
+#define REP(i,n) for (int i = 1; i <= n; i++)
+#define mod 1000000007
+#define pb push_back
+#define ff first
+#define ss second
+#define ii pair<int,int>
+#define vi vector<int>
+#define vii vector<ii>
+#define lli long long int
+#define endl '\n'
+using namespace std;
+int ar[200001];
+
+int getMax1(int n)
+{
+	int cnt = 1;
+	for(int i=n-1;i>=1;i--)
+	if(ar[i] <= ar[i+1])
+	cnt++;
+	else
+	break;
+	
+	return cnt;
+}
+
+int getMax2(int n)
+{
+	int cnt = 1;
+	for(int i=n-1;i>=1;i--)
+	if(ar[i] >= ar[i+1]) cnt++;
+	else
+	break;
+	
+	return cnt;
+}
+
+int getMax3(int n)
+{
+	int cnt = 1;
+	
+	int i = n-1;
+	for(;i>=1;i--)
+	{
+		if(ar[i] >= ar[i+1]) cnt++;
+		else
+		break;
+	}
+	
+	for(;i>=1;i--)
+	{
+		if(ar[i] <= ar[i+1]) cnt++;
+		else
+		break;
+	}
+	
+	return cnt;
+}
+
+int main()
+{
+	int t , n , mx;
+	cin>>t;
+	while(t--)
+	{
+		cin>>n;
+		REP(i , n) cin>>ar[i];
+		
+		mx = 1;
+		mx = max(mx , getMax1(n));
+		mx = max(mx , getMax2(n));
+		mx = max(mx , getMax3(n));
+		
+		
+		cout<<n-mx<<endl;
+	}
+}
diff --git a/Codeforces/Editorials/Greedy Algorithms/Move Brackets.cpp b/Codeforces/Editorials/Greedy Algorithms/Move Brackets.cpp
new file mode 100644
index 0000000..dbc610a
--- /dev/null
+++ b/Codeforces/Editorials/Greedy Algorithms/Move Brackets.cpp	
@@ -0,0 +1,55 @@
+/*
+ * Problem Name : C. Move Brackets
+ * Problem Link : https://codeforces.com/problemset/problem/1374/C
+ * Video solution link : https://youtu.be/g6HhBoXv50I
+ * Write here if video solution doesn't exist : icodencode@gmail.com
+ * Channel name & link : CodeNCode (https://www.youtube.com/@codencode)
+ */
+
+#include<bits/stdc++.h>
+#define REP(i,n) for (int i = 1; i <= n; i++)
+#define mod 1000000007
+#define pb push_back
+#define ff first
+#define ss second
+#define ii pair<int,int>
+#define vi vector<int>
+#define vii vector<ii>
+#define lli long long int
+#define endl '\n'
+using namespace std;
+char ar[1000001];
+int n;
+
+int getAns()
+{
+	stack<char> st;
+	
+	REP(i , n)
+	{
+		if(ar[i] == '(')
+		st.push('(');
+		else
+		{
+			if(!st.empty() && st.top() == '(') st.pop();
+			else
+			st.push(')');
+		}
+	}
+	
+	return st.size();
+}
+
+int main()
+{
+	int t;
+	cin>>t;
+	
+	while(t--)
+	{
+		cin>>n;
+		REP(i , n) cin>>ar[i];
+		
+		cout<<(getAns())/2<<endl;
+	}
+}
diff --git a/Codeforces/Editorials/Greedy Algorithms/Pluses and Minuses.cpp b/Codeforces/Editorials/Greedy Algorithms/Pluses and Minuses.cpp
new file mode 100644
index 0000000..4bdd1d9
--- /dev/null
+++ b/Codeforces/Editorials/Greedy Algorithms/Pluses and Minuses.cpp	
@@ -0,0 +1,62 @@
+/*
+ * Problem Name : C. Pluses and Minuses
+ * Problem Link : https://codeforces.com/problemset/problem/1373/C
+ * Video solution link : https://youtu.be/YewVnTMnxaE
+ * Write here if video solution doesn't exist : icodencode@gmail.com
+ * Channel name & link : CodeNCode (https://www.youtube.com/@codencode)
+ */
+
+#include<bits/stdc++.h>
+#define REP(i,n) for (int i = 1; i <= n; i++)
+#define mod 1000000007
+#define pb push_back
+#define ff first
+#define ss second
+#define ii pair<int,int>
+#define vi vector<int>
+#define vii vector<ii>
+#define lli long long int
+#define endl '\n'
+using namespace std;
+int ar[1000001];
+map<int,int> mp;
+
+int getCnt(int key)
+{
+	return mp[key];
+}
+
+int main()
+{
+	lli t , res;
+	string st;
+	cin>>t;
+	while(t--)
+	{
+		cin>>st;
+		mp.clear();
+		
+		res = 0;
+		int mx = 0;
+		int cnt = 0;
+		for(int i=0;i<st.size();i++)
+		{
+			char ch = st[i];
+			if(ch == '-') cnt--;
+			else		  cnt++;
+			
+			ar[i+1] = cnt;
+			if(cnt < 0 && mp.find(cnt) == mp.end()) mp[cnt] = i+1;
+			
+			mx = min(mx , cnt);
+		}
+		
+		mx *= -1;
+		
+		for(int i=0;i<mx;i++)
+		{
+			res += getCnt(-(i+1));
+		}
+		cout<<res+st.size()<<endl;
+	}
+}
\ No newline at end of file
diff --git a/Codeforces/Editorials/Greedy Algorithms/RationalLee.cpp b/Codeforces/Editorials/Greedy Algorithms/RationalLee.cpp
new file mode 100644
index 0000000..05fd001
--- /dev/null
+++ b/Codeforces/Editorials/Greedy Algorithms/RationalLee.cpp	
@@ -0,0 +1,59 @@
+/*
+ * Problem Name : C. RationalLee
+ * Problem Link : https://codeforces.com/contest/1369/problem/C
+ * Video solution link : https://youtu.be/QCzl0XwwKhE
+ * Write here if video solution doesn't exist : icodencode@gmail.com
+ * Channel name & link : CodeNCode (https://www.youtube.com/@codencode)
+ */
+
+#include<bits/stdc++.h>
+#define REP(i,n) for (int i = 1; i <= n; i++)
+#define mod 1000000007
+#define pb push_back
+#define ff first
+#define ss second
+#define ii pair<int,int>
+#define vi vector<int>
+#define vii vector<ii>
+#define lli long long int
+#define INF 1000000000
+#define endl '\n'
+const double PI = 3.141592653589793238460;
+typedef std::complex<double> Complex;
+typedef std::valarray<Complex> CArray;
+
+using namespace std;
+lli ar[200001] , br[200001];
+int main()
+{
+	int t , n , k;
+	cin>>t;
+	while(t--)
+	{
+		cin>>n>>k;
+		REP(i , n) cin>>ar[i];
+		REP(i , k) cin>>br[i];
+		
+		sort(ar+1 , ar+n+1);
+		sort(br+1 , br+k+1);
+		
+		lli res = 0;
+		int i = 1;
+		int j = n;
+		int p = 1;
+		
+		while(p <= k && br[p] == 1)
+		res += 2 * ar[j] , j-- , p++;
+		
+		for(int q=k;q>=p;q--)
+		{
+			res += ar[j] + ar[i];
+			j-- , i++ , br[q] -= 2;
+			
+			while(br[q] > 0)
+			i++ , br[q]--;
+		}
+		
+		cout<<res<<endl;
+	}
+}
diff --git a/Codeforces/Editorials/SQRT & Mo's Algorithm/D. Cut and Stick.cpp b/Codeforces/Editorials/SQRT & Mo's Algorithm/D. Cut and Stick.cpp
new file mode 100644
index 0000000..6bec960
--- /dev/null
+++ b/Codeforces/Editorials/SQRT & Mo's Algorithm/D. Cut and Stick.cpp	
@@ -0,0 +1,128 @@
+/*
+ * Problem Name : D. Cut and Stick
+ * Problem Link : https://codeforces.com/contest/1514/problem/D
+ * Video solution link : https://youtu.be/zNadd6gLuAA
+ * Write here if video solution doesn't exist : icodencode@gmail.com
+ * Channel name & link : CodeNCode (https://www.youtube.com/@codencode)
+ */
+
+#include<bits/stdc++.h>
+#define REP(i,n) for (int i = 1; i <= n; i++)
+#define mod 1000000007
+#define pb push_back
+#define ff first
+#define ss second
+#define ii pair<int,int>
+#define vi vector<int>
+#define vii vector<ii>
+#define lli long long int
+#define INF 1000000000
+#define endl '\n'
+#define BLOCK 555
+const double PI = 3.141592653589793238460;
+typedef std::complex<double> Complex;
+typedef std::valarray<Complex> CArray;
+ 
+using namespace std;
+struct query{
+	int l;
+	int r;
+	int i;
+};
+query Q[300001];
+int ar[300001] , ans[300001];
+int fre[300001];
+
+int freOfFre[300001];
+int currMax = 0;
+ 
+bool comp(query a , query b)
+{
+	if(a.l / BLOCK != b.l/BLOCK)
+	return a.l/BLOCK < b.l/BLOCK;
+	
+	return a.r < b.r;
+}
+
+void add(int pos)
+{
+	int preF = fre[ar[pos]];
+	fre[ar[pos]]++;
+	int currF = fre[ar[pos]];
+	
+	freOfFre[preF]--;
+	freOfFre[currF]++;
+	
+	if(currF > currMax)
+	{
+		currMax = currF;
+	}
+}
+ 
+void remove(int pos)
+{
+	int preF = fre[ar[pos]];
+	fre[ar[pos]]--;
+	int currF = fre[ar[pos]];
+	
+	freOfFre[preF]--;
+	freOfFre[currF]++;
+	
+	if(currF < currMax)
+	{
+		while(freOfFre[currMax] == 0)
+		currMax--;
+	}
+}
+ 
+int main()
+{
+	
+	ios_base::sync_with_stdio(false);
+	cin.tie(0);
+	cout.tie(0);
+	
+	int n , q;
+	cin>>n>>q;
+	for(int i=0;i<n;i++)
+	cin>>ar[i];
+	
+	for(int i=0;i<q;i++){
+		cin>>Q[i].l>>Q[i].r;
+		Q[i].i = i , Q[i].l-- , Q[i].r--;
+	}
+	
+	sort(Q , Q+q , comp);
+	int ML = 0 , MR = -1;
+	for(int i=0;i<q;i++)
+	{
+		int L = Q[i].l;
+		int R = Q[i].r;
+		
+		while(ML > L)
+		ML-- , add(ML);
+		
+		while(MR < R)
+		MR++ , add(MR);
+		
+		while(ML < L)
+		remove(ML) , ML++;
+		
+		while(MR > R)
+		remove(MR) , MR--;
+		
+		int total = Q[i].r - Q[i].l + 1;
+		int rem = total - currMax;
+		int half = (total+1)/2;
+		
+		if(currMax <= half)
+		ans[Q[i].i] = 1;
+		else
+		{
+			ans[Q[i].i] = total - 2*rem;
+		}
+	}
+	
+	for(int i=0;i<q;i++)
+	cout<<ans[i]<<'\n';
+}
\ No newline at end of file
diff --git a/README.md b/README.md
index 9fdcefd..4cbfc77 100644
--- a/README.md
+++ b/README.md
@@ -13,30 +13,30 @@ I have courses like Number theory and graph theory course which start from basic
 
 ## 📺 Latest YouTube Videos
 <!-- YOUTUBE:START -->
-- [L01 : Orientation of 3 points | Geometric Algorithm | CodeNCode](https://www.youtube.com/watch?v=IwKkiaoqwTc)
-- [E007 : Counting Bits using DP | Bit Manipulation | CodeNCode](https://www.youtube.com/watch?v=oidrF6nx01s)
-- [E006 : The Sports Festival | Dynamic Programming | CodeNCode](https://www.youtube.com/watch?v=_AcGinQvK44)
-- [E006 : Binary Literacy | Constructive Algorithms | CodeNCode](https://www.youtube.com/watch?v=1JEpe7wl1u4)
-- [E002 : ADA and pet | String Algorithms | SPOJ](https://www.youtube.com/watch?v=oj5EWo7PL9M)
+- [L13: Observer Pattern | Design Patterns](https://www.youtube.com/watch?v=N7qNtyHTh5c)
+- [5 Most Important Topics you must cover for SDE1 Amazon Interview #programming #coding](https://www.youtube.com/shorts/x6IKa96a09w)
+- [L12: Flyweight Pattern | Design Patterns](https://www.youtube.com/watch?v=x-VGZUwfev0)
+- [Java design pattern course update #coding #programming #java #designpatternsinjava #designpatterns](https://www.youtube.com/shorts/P6HOll3evSM)
+- [L11 : Composite Pattern | Design Patterns](https://www.youtube.com/watch?v=MPePQaMPlBs)
 <!-- YOUTUBE:END -->
 
 
 ## List of Courses by CodeNCode 
-- [Basic Algorithms](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik5HC7D3gUwc8cqwDtvOaqke)
+- [Basic Algorithms](https://www.youtube.com/playlist?list=PL5DyztRVgtRW09egS6AY2oTVwF_5MfdRj)
 - [Bit Manipulation](https://www.youtube.com/playlist?list=PL5DyztRVgtRUVORP3AXvX91uovcaZv0q9)
-- [Combinatorics](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik48tGHU2eJxQdnGls2QPCBl)
+- [Combinatorics](https://www.youtube.com/playlist?list=PL5DyztRVgtRXRA-AEcBI4kfs42Aq9P1kr)
 - [Disjoint Set Union](https://www.youtube.com/playlist?list=PL5DyztRVgtRVIAoYAKanON01SM7tVr8PE)
 - [Dynamic Programming Part 1](https://www.youtube.com/playlist?list=PL5DyztRVgtRVr1katnCAdGdp02nJrDHv6)
 - [Dynamic Programming Part 2](https://www.youtube.com/playlist?list=PL5DyztRVgtRV-t64WnLKpuDjDbH7xNmnW)
 - [Graph Theory Part 1](https://www.youtube.com/playlist?list=PL5DyztRVgtRVLwNWS7Rpp4qzVVHJalt22)
 - [Graph Theory Part 2](https://www.youtube.com/playlist?list=PL5DyztRVgtRW0Kdd8i1xML7t-ge56XRQR)
 - [Number Theory](https://www.youtube.com/playlist?list=PL5DyztRVgtRWblnyEHtajWijQffrfwLz6)
-- [Queries On Trees](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik4mjMTt7Po4DocBBI_Ai6s8)
+- [Queries On Trees](https://www.youtube.com/playlist?list=PL5DyztRVgtRVQsDZIJKYLYOj9uX9yluNJ)
 - [Recursion](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik7Vp1iJw2V57MT4UVdZDoWj)
-- [Segment Tree](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik6v2-emg_JGcC9v2v2YTbvq)
+- [Segment Tree](https://www.youtube.com/playlist?list=PL5DyztRVgtRWt0Kgy7fCN9OSPgr6AI3DO)
 - [String Algorithms](https://www.youtube.com/playlist?list=PL5DyztRVgtRWVqLox_K8lrWZCclxzHzLD)
-- [Mo's Algorithm & SQRT Decomposition](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik6DCzm9XZJbNwyHtHGclcEh)
-- [Geometric Algorithms](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik7OAGWIMYrgRkKqshRBpJoY)
+- [Mo's Algorithm & SQRT Decomposition](https://www.youtube.com/playlist?list=PL5DyztRVgtRWtz6J5culNvZzeX5nnoZ7r)
+- [Geometric Algorithms](https://www.youtube.com/playlist?list=PL5DyztRVgtRVHE6fulR_q0W_pNd8JdMlb)
 
 
 # Video Editorials : By Platform
@@ -84,14 +84,14 @@ I have courses like Number theory and graph theory course which start from basic
 - [Binary Search](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik6LzOqo8V3GwthSd9GIN_CK)
 
 ## SPOJ
-- [Number Theory](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik50mPNfoadAHoCnjeW2Jsw0)
-- [Graph & Tree](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik5niWOljO7dQVn0o-zf_f9_)
-- [Binary Search](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik609P408nEkgYjgE12gFcyx)
-- [Segment Tree](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik5ihRT6oH2ztAYMnGBQ4gSa)
-- [String Algorithms](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik5xR-rGBIiP-1V2uK0GZpTT)
+- [Number Theory](https://www.youtube.com/playlist?list=PL5DyztRVgtRUeSPcvsTxVAdr7Jrp3S2oq)
+- [Graph & Tree](https://www.youtube.com/playlist?list=PL5DyztRVgtRXNt92h6JfzKKf7EweRNWyf)
+- [Binary Search](https://www.youtube.com/playlist?list=PL5DyztRVgtRWA58PlawGcA9-FVcdnJe3N)
+- [Range Queries](https://www.youtube.com/playlist?list=PL5DyztRVgtRXQh9YUYhIbBvg-UrGJFAry)
+- [String Algorithms](https://www.youtube.com/playlist?list=PL5DyztRVgtRWOFCsK0khl_oXdOHkSgGoc)
 - [Others](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik5rJQUqzgHdlmK7MSR4n8AK)
 
 ## Hackerrank
-- [Bit Manipulation](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik4hYJ1dykHIJ68GR_Of8WiK)
+- [Bit Manipulation](https://www.youtube.com/playlist?list=PL5DyztRVgtRVOMi_HXpUXOje3rPbUdmez)
 - [Number Theory](https://www.youtube.com/playlist?list=PL2q4fbVm1Ik7HIi2yVU1eIZN-mNDyBYMv)
 
diff --git a/SPOJ/Binary Search/ABCDEF.cpp b/SPOJ/Binary Search/ABCDEF.cpp
new file mode 100644
index 0000000..2fbf7ac
--- /dev/null
+++ b/SPOJ/Binary Search/ABCDEF.cpp	
@@ -0,0 +1,59 @@
+/*
+ * Problem Name : ABCDEF
+ * Problem Link : https://www.spoj.com/problems/ABCDEF/
+ * Video solution link : https://youtu.be/07rX0DjWSdY
+ * Write here if video solution doesn't exist : icodencode@gmail.com
+ * Channel name & link : CodeNCode (https://www.youtube.com/@codencode)
+ */
+
+#include<bits/stdc++.h>
+#define REP(i,n) for (int i = 1; i <= n; i++)
+#define mod 1000000007
+#define pb push_back
+#define ff first
+#define ss second
+#define ii pair<int,int>
+#define vi vector<int>
+#define vii vector<ii>
+#define lli long long int
+#define INF 1000000000
+#define endl '\n'
+const double PI = 3.141592653589793238460;
+typedef std::complex<double> Complex;
+typedef std::valarray<Complex> CArray;
+using namespace std;
+ 
+int ar[100];
+int main()
+{
+	int n;
+	map<int,int> mp;
+	cin>>n;
+	
+	for(int i=0;i<n;i++) cin>>ar[i];
+	
+	for(int f=0;f<n;f++)
+	{
+		for(int e=0;e<n;e++)
+		{
+			for(int d=0;d<n;d++) {
+				if(ar[d] == 0) continue;
+				mp[(ar[e] + ar[f]) * ar[d]]++;
+			}
+		}
+	}
+	
+	lli res = 0;
+	
+	for(int a=0;a<n;a++)
+	{
+		for(int b=0;b<n;b++)
+		{
+			for(int c=0;c<n;c++) res += mp[(ar[a] * ar[b]) + ar[c]];
+		}
+	}
+	
+	cout<<res;
+	
+}
+ 
diff --git a/SPOJ/Binary Search/AGGRCOW - Aggressive cows.cpp b/SPOJ/Binary Search/AGGRCOW - Aggressive cows.cpp
new file mode 100644
index 0000000..a61f9d4
--- /dev/null
+++ b/SPOJ/Binary Search/AGGRCOW - Aggressive cows.cpp	
@@ -0,0 +1,74 @@
+/*
+ * Problem Name : AGGRCOW - Aggressive cows
+ * Problem Link : https://www.spoj.com/problems/AGGRCOW/
+ * Video solution link : https://youtu.be/lLA0BW_f8v0
+ * Write here if video solution doesn't exist : icodencode@gmail.com
+ * Channel name & link : CodeNCode (https://www.youtube.com/@codencode)
+ */
+
+#include<bits/stdc++.h>
+#define REP(i,n) for (int i = 1; i <= n; i++)
+#define mod 1000000007
+#define pb push_back
+#define ff first
+#define ss second
+#define ii pair<int,int>
+#define vi vector<int>
+#define vii vector<ii>
+#define lli long long int
+#define INF 1000000000
+#define endl '\n'
+const double PI = 3.141592653589793238460;
+typedef std::complex<double> Complex;
+typedef std::valarray<Complex> CArray;
+ 
+using namespace std;
+int ar[100001];
+ 
+bool isValid(int mid , int C , int n)
+{
+	int cnt = 0;
+	int pre = -INF;
+	
+	for(int i=1;i<=n;i++)
+	if(ar[i] - pre >= mid)
+	cnt++ , pre = ar[i];
+	
+	if(cnt >= C) return true;
+	else		 return false;
+}
+ 
+int getAns(int n , int c)
+{
+	int L = 0;
+	int H = ar[n] - ar[1];
+	
+	int ans = 0;
+	
+	while(L <= H)
+	{
+		int mid = (L + H) / 2;
+		
+		if(isValid(mid , c , n))
+		ans = max(ans , mid) , L = mid + 1;
+		else
+		H = mid - 1;
+	}
+	
+	return ans;
+}
+ 
+int main()
+{
+	int t , n , c;
+	cin>>t;
+	while(t--)
+	{
+		cin>>n>>c;
+		for(int i=1;i<=n;i++)
+		cin>>ar[i];
+		
+		sort(ar + 1 , ar + n + 1);
+		cout<<getAns(n , c)<<endl;
+	}
+}
diff --git a/SPOJ/Graph & Tree/SUBMERGE.cpp b/SPOJ/Graph & Tree/SUBMERGE.cpp
new file mode 100644
index 0000000..14718c7
--- /dev/null
+++ b/SPOJ/Graph & Tree/SUBMERGE.cpp	
@@ -0,0 +1,83 @@
+/*
+ * Problem Name : SUBMERGE - Submerging Islands
+ * Problem Link : https://www.spoj.com/problems/SUBMERGE/
+ * Video solution link : https://youtu.be/sFLFU6wTVls
+ * Write here if video solution doesn't exist : icodencode@gmail.com
+ * Channel name & link : CodeNCode (https://www.youtube.com/@codencode)
+ */
+
+#include<bits/stdc++.h>
+using namespace std;
+
+const int N = 1e4;
+vector<int> adj[N+1];
+bool vis[N+1];
+bool isArticulationPoint[N+1];
+int in[N+1] , low[N+1];
+int timer;
+int result;
+
+void clear(int n){
+	for(int i=1;i<=n;i++){
+		adj[i].clear();
+		vis[i] = isArticulationPoint[i] = false;
+	}
+	timer = result = 0;
+}
+
+void dfs(int node , int par){
+	vis[node] = true;
+	in[node] = low[node] = timer++;
+	int child = 0;
+
+	for(int v : adj[node]){
+		if(v == par) continue;
+
+		if(vis[v]){
+			low[node] = min(low[node] , in[v]);
+		}else{
+			child++ , dfs(v , node);
+			if(par != -1 && low[v] >= in[node]){
+				if(isArticulationPoint[node] == false){
+					isArticulationPoint[node] = true;
+					result++;
+				}
+			}
+			low[node] = min(low[node] , low[v]);
+		}
+	}
+
+	if(par == -1 && child > 1){
+		if(isArticulationPoint[node] == false){
+			isArticulationPoint[node] = true;
+			result++;
+		}
+	}
+
+}
+
+int main(){
+	#ifndef ONLINE_JUDGE
+		freopen("input.txt" , "r" , stdin);
+		freopen("output.txt" , "w" , stdout);
+	#endif
+
+	int n , m;
+	int a , b;
+
+	while(1){
+		cin>>n>>m;
+		if(n == 0 && m == 0) break;
+
+		clear(n);
+
+		for(int i=1;i<=m;i++){
+			cin>>a>>b;
+			adj[a].push_back(b);
+			adj[b].push_back(a);
+		}
+
+		dfs(1 , -1);
+		cout<<result<<"\n";
+	}
+}
\ No newline at end of file
diff --git a/SPOJ/Number Theory/POLYMUL - Polynomial Multiplication.cpp b/SPOJ/Number Theory/POLYMUL - Polynomial Multiplication.cpp
new file mode 100644
index 0000000..bb706c3
--- /dev/null
+++ b/SPOJ/Number Theory/POLYMUL - Polynomial Multiplication.cpp	
@@ -0,0 +1,119 @@
+/*
+ * Problem Name : POLYMUL - Polynomial Multiplication
+ * Problem Link : https://www.spoj.com/problems/POLYMUL/
+ * Video solution link : https://youtu.be/Ki3r6CaVI3U
+ * Write here if video solution doesn't exist : icodencode@gmail.com
+ * Channel name & link : CodeNCode (https://www.youtube.com/@codencode)
+ */
+
+
+#include<bits/stdc++.h>
+#define vi vector<int>
+#define ll long long
+#define mod 1000000007
+using namespace std;
+
+// complex # = a + ib
+using cd = complex<double>;
+const double PI = acos(-1);
+
+vector<cd> fft(vector<cd> p, int n) {
+	if(n == 1) return p;
+	
+	vector<cd> Pe, Po;
+	
+	for(int i=0; 2*i<n;i++){
+		Pe.push_back(p[2*i]);
+		Po.push_back(p[2*i + 1]);
+	}
+	
+	Pe = fft(Pe, n/2);
+	Po = fft(Po, n/2);
+	
+	double ang = (2 * PI) / n;
+	
+	// w^0 = 1 + 0i
+	// w^1 = cos(ang) + isin(ang)
+	cd w(1), w_delta(cos(ang), sin(ang));
+	
+	for(int i=0; i< n/2;i++){
+		p[i] = Pe[i] + w * Po[i];
+		p[i + n/2] = Pe[i] - w * Po[i];
+		
+		w *= w_delta;
+	}
+	
+	return p;
+}
+
+vector<cd> inversefft(vector<cd> p, int n) {
+	if(n == 1) return p;
+	
+	vector<cd> Pe, Po;
+	
+	for(int i=0; 2*i<n;i++){
+		Pe.push_back(p[2*i]);
+		Po.push_back(p[2*i + 1]);
+	}
+	
+	Pe = inversefft(Pe, n/2);
+	Po = inversefft(Po, n/2);
+	
+	double ang = (-2 * PI) / n;
+	
+	// w^0 = 1 + 0i
+	// w^1 = cos(ang) + isin(ang)
+	cd w(1), w_delta(cos(ang), sin(ang));
+	
+	for(int i=0; i < n/2;i++){
+		p[i] = (Pe[i] + w * Po[i]);
+		p[i + n/2] = (Pe[i] - w * Po[i]);
+		
+		w *= w_delta;
+	}
+	
+	return p;
+}
+
+vector<long> multiply(vector<int> &a, vector<int> &b) {
+	vector<cd> fa(a.begin(), a.end()), fb(b.begin(), b.end());
+	
+	// finding nearest power of 2.
+	int n = 1;
+	while(n < a.size() + b.size()) n <<= 1;
+	fa.resize(n), fb.resize(n);
+	
+	// Evaluating Polynomials.
+	fa = fft(fa, n);
+	fb = fft(fb, n);
+	
+	// Multiplying Polynomials.
+	for(int i=0;i<n;i++) fa[i] *= fb[i];
+	
+	// Converting value form to coefficient form.
+	fa = inversefft(fa, n);
+	
+	vector<long> res(n);
+	for(int i=0;i<n;i++) res[i] = round(fa[i].real() / n);
+	
+	return res;
+}
+
+int  main(){
+	int n, t;
+	
+	cin>>t;
+	
+	while(t--){
+		cin>>n;
+		vector<int> a(n+1), b(n+1);
+		
+		for(int i=0;i<=n;i++) cin>>a[i];
+		for(int i=0;i<=n;i++) cin>>b[i];
+		
+		vector<long> res = multiply(a, b);
+		
+		for(int i=0;i<=2*n;i++) cout<<res[i]<<" ";
+		cout<<endl;
+	}
+}