75. Sort Colors

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.

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

分析

实际上就是使用快排去做，升序

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class Solution { public:     void sortColors(vector<int>& nums) {         sortHelper(nums, 0, nums.size() - 1);     }           void sortHelper(vector<int> & nums, int left, int right){         if(left >= right) return;         int i = left, j = right;         int key = nums[(left + right) / 2];         while(i <= j){             while(i <= j && nums[i] < key) ++i;             while(i <= j && nums[j] > key) --j;             if(i <= j){                 int tmp = nums[i];                 nums[i++] = nums[j];                 nums[j--] = tmp;             }         }         sortHelper(nums, left, j);         sortHelper(nums, i, right);     } };

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