SortColors.java

//https://leetcode.com/problems/sort-colors/

// Given an array nums with n objects colored red, white, or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white, and blue.

// We will use the integers 0, 1, and 2 to represent the color red, white, and blue, respectively.

 

// Example 1:

// Input: nums = [2,0,2,1,1,0]
// Output: [0,0,1,1,2,2]
// Example 2:

// Input: nums = [2,0,1]
// Output: [0,1,2]
// Example 3:

// Input: nums = [0]
// Output: [0]
// Example 4:

// Input: nums = [1]
// Output: [1]
 

// Constraints:

// n == nums.length
// 1 <= n <= 300
// nums[i] is 0, 1, or 2.



class Solution {
    public void sortColors(int[] nums) {
        int redPointer = 0, whitePointer = 0, bluePointer = nums.length - 1;
        while(whitePointer<=bluePointer){
            if(nums[whitePointer]==2){
                int temp = nums[whitePointer];
                nums[whitePointer] = nums[bluePointer];
                nums[bluePointer] = temp;
                bluePointer--;
                continue;
            }
            if(nums[whitePointer]==1){
                whitePointer++;
                continue;
            }
            if(nums[whitePointer]==0){
                int temp = nums[whitePointer];
                nums[whitePointer] = nums[redPointer];
                nums[redPointer] = temp;
                whitePointer++;
                redPointer++;
                continue;
            }
        }
        
    }