Sort Colors

Sort the array in place so that the elements of the same color are adjacent, with the colors in the order of red, white, and blue. The function should return the same array.

Sort the array in place so that the elements of the same color are adjacent, with the colors in the order of red, white, and blue. The function should return the same array.

Statement

Given an array, colors, which contains a combination of the following three elements:

• 0 (representing red)
• 1 (representing white)
• 2 (representing blue)

Sort the array in place so that the elements of the same color are adjacent, with the colors in the order of red, white, and blue. The function should return the same array.

Note: The function should only return the modified colors array.

Constraints

• 1 ≤ colors.length ≤ 300
• colors[i] can only contain 0s, 1s, or 2s.

Examples

Example 1

Input: colors = [2, 0, 2, 1, 1, 0] Output: [0, 0, 1, 1, 2, 2]

Example 2

Input: colors = [2, 0, 1] Output: [0, 1, 2]

Solution

We'll care three pointer low, mide and high , our primary focus will be on mid we'll check comparison with mid and swap accordingly , One edge case need to be keept in mide while solving this whenever mid receives 2 and we swap it with high we do not increment the value of low because we are not sure what value we got from high.

function sortColors(arr) {
    let low = 0;      // boundary for 0s
    let mid = 0;       // current element being examined
    let high = arr.length - 1;  // boundary for 2s

    while (mid <= high) {
        if (arr[mid] === 0) {
            [arr[low], arr[mid]] = [arr[mid], arr[low]];
            low++;
            mid++;
        } else if (arr[mid] === 1) {
            mid++;
        } else { // arr[mid] === 2
            [arr[mid], arr[high]] = [arr[high], arr[mid]];
            high--;
            // note: mid is NOT incremented here
        }
    }

    return arr;
}

console.log(sortColors([2, 0, 2, 1, 1, 0])); // [0, 0, 1, 1, 2, 2]