Leetcode: 75. Sort Colors

Description

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

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

Note:
You are not suppose to use the library's sort function for this problem.

思路

• 跟快排的partition一个思想，两个index,一个从前往后，一个从后往前，前面这个对应0， 后面那个对应2

代码

class Solution {
public:
    void sortColors(vector<int>& nums) {
        int len = nums.size();
        if(len <= 1) return;
        
        int index_red = -1, index_blue = len;
        int i = 0;
        while(i < index_blue){
            if(nums[i] == 0){
                index_red++;
                swap(nums[i], nums[index_red]);
            }else if(nums[i] == 2){
                index_blue--;
                swap(nums[i], nums[index_blue]);
                continue;
            }
        
            i++;
        }
    }
};