Leetcode - 443. String Compression

Need to update the solution

Please read the question completely before going through the solution

This video clearly explains a two pointer approach to solve the problem

It starts with initialising the first pointer , second pointer at index 0 of array and then for each of char (ie the char at first pointer) second pointer is moved till we find a mismatch in characters at first and second pointer.

index variable is used to track the current position of updated character array , after each char entry index is forwarded to next position , and the count entry of count j-i is done only when count is more than 1 .

/**
 * @param {character[]} chars
 * @return {number}
 */

var compress = function(chars) {
    let index = 0;
    let i = 0;
    let j = 0;
    while(i<chars.length){
        j=i;
        while(j<chars.length && chars[i] === chars[j]){
            j++
        }

        chars[index++] = chars[i];
        let count = (j - i) ;
        if (count > 1) {
            let str = count.toString(); // Convert count to string
            for (let digit of str) {
                chars[index++] = digit;
            }
        }
        i=j; 
    }
    return index
};

/**
 * @param {character[]} chars
 * @return {number}
 */
var compress = function(chars) {
  let n = chars.length;
    if (n <= 1) {
        return n; // For arrays of length 0 or 1, no compression needed
    }

    let index = 0; // Position in the compressed array
    let counter = 1;

    for (let i = 1; i <= n; i++) {
        if (chars[i] === chars[i - 1]) {
            counter++;
        } else {
            // Place the character at the current index
            chars[index++] = chars[i - 1]; 

            // Place the count if it's greater than 1
            if (counter > 1) {
                for (let digit of counter.toString()) {
                    chars[index++] = digit;
                }
            }

            // Reset counter
            counter = 1;
        }
    }

    return index; // Length of the compressed array
};

Syntax Learnings

1. index++ is a post increment operator , it first assign the value and then increments
2. num can be converted to string by .toString() method