JavaScript Print shortest Path to Print a String on Screen

Given a screen with the English alphabet (A-Z) and a remote control with navigation keys (left, right, up, down), we have to determine the most efficient way to write a string using the remote. Starting from the top-left corner of the screen, we need to move through the alphabet to spell out the entire input string in the correct order. In this article, we will see how to find the shortest path to print a string by using Javascript.

Screen: 

A B C D E
F G H I J
K L M N O
P Q R S T
U V W X Y
Z

Example: 

Input: “HELLO”
Output: 
Right
Right
OK
Up
Right
Right
OK
Left
Left
Left
Down
Down
OK
OK
Right
Right
Right
OK

The idea is to consider the screen as a 2D matrix of characters. Then we consider all characters of a given string one by one and print out the shortest path between the current character and the next character in the matrix. In order to find the shortest path, we consider the coordinates of the current character and the next character in the matrix. Based on the difference between x and y values of the current and next character’s coordinates, we move left, right, top, or bottom. i.e.

If row difference is negative, we move up
If row difference is positive, we move down
If column difference is negative, we go left
If column difference is positive, we go right

Example: In this Example, we will find shortest path to print a string on screen by using javascript.

// Function to print the shortest 
// possible path to type a given inputString

function printShortestPathToTypeString(inputString) {
    // Initialize current position (0, 0) 
    // and index for the inputString
    let currentIndex = 0;
    let currentX = 0, currentY = 0;

    // Loop through the inputString
    while (currentIndex < inputString.length) {
        // Calculate the next position coordinates
        let nextX = parseInt
            ((inputString[currentIndex].charCodeAt()
                - 'A'.charCodeAt()) / 5, 10);
        let nextY = (inputString[currentIndex].charCodeAt()
            - 'B'.charCodeAt() + 1) % 5;

        // Move Up
        while (currentX > nextX) {
            console.log("Up");
            currentX--;
        }

        // Move Left
        while (currentY > nextY) {
            console.log("Left");
            currentY--;
        }

        // Move Down
        while (currentX < nextX) {
            console.log("Down");
            currentX++;
        }

        // Move Right
        while (currentY < nextY) {
            console.log("Right");
            currentY++;
        }

        // Press OK to type the character
        console.log("OK");
        currentIndex++;
    }
}

// Driver code
let inputString = "HELLO";
printShortestPathToTypeString(inputString);

Down
Right
Right
OK
Up
Right
Right
OK
Left
Left
Left
Down
Down
OK
OK
Right
Right
Right
OK

Time Complexity: O(n*n)

Auxiliary Space: O(1)