Dutch National Flag Problem

Given an array containing 0s, 1s and 2s, sort the array in-place. You should treat numbers of the array as objects, hence, we can’t count 0s, 1s, and 2s to recreate the array.

The flag of the Netherlands consists of three colors: red, white and blue; and since our input array also consists of three different numbers that is why it is called Dutch National Flag problem.

Example 1:

• Input: nums = [2,0,2,1,1,0]
• Output: [0, 0, 1, 1, 2]

class Solution {
    public void sortColors(int[] nums) {
        var low = 0;
        var high = nums.length - 1;
        for (int i = 0; i <= high;) {
            var val = nums[i];
            if (val == 0) {
                swap(nums, i, low);
                low ++;
                i ++;
            } else if (val == 2) {
                swap(nums, i, high);
                high --;
            } else {
                i ++;
            }
        }
    }

    private void swap(int[] nums, int x, int y) {
        var t = nums[x];
        nums[x] = nums[y];
        nums[y] = t;
    }
}