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.
解题思路:
仿照快排的partition解题,调用三次即可解决问题,复杂度O(n)
class Solution {
public:
void sortColors(vector<int>& nums) {
int mid = partition(nums, 1, 0, nums.size() - 1);
partition(nums, 0, 0, mid);
partition(nums, 2, mid, nums.size() - 1);
}
int partition(vector<int>& nums, int pivot, int begin, int end) {
//int end = nums.size() - 1;
while(end > begin){
while(end > begin && nums[end] >= pivot) --end;
while(end > begin && nums[begin] < pivot) ++begin;
int tmp = nums[begin];
nums[begin] = nums[end];
nums[end] = tmp;
}
return begin;
}
};
结果: