p18.java

/*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.

You must solve this problem without using the library's sort function.


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]
 

Constraints:

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

Follow up: Could you come up with a one-pass algorithm using only constant extra space?*/
class Solution {
    public void sortColors(int[] nums) {
        int l=0;
        int m=0;
        int h=nums.length-1;
        int temp;
        while(m<=h){
            if(nums[m]==0){
                temp=nums[l];
                nums[l]=nums[m];
                nums[m]=temp;
                l++;
                m++;
            }
            else if(nums[m]==1){
                m++;
            }
            else{
                temp=nums[m];
                nums[m]=nums[h];
                nums[h]=temp;
                h--;
            }
        }
    }
}