Leetcode_c++： Sort Colors (075）

题目

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.

算法

two指针

复杂度：O（N）

题意就是对一个包含0,1,2三种数字的数组重新排序，使得排好序的数组前一段都是0，中间一段都是1，最后一段都是2。

class Solution {
public:
void sortColors(vector<int>& nums) {
int n=nums.size();
int zeropoint=0,twopoint=n-1;
int i=0;
while(i<=twopoint){
if(nums[i]==0 && i!=zeropoint)
swap(nums[zeropoint++],nums[i]);
else if(nums[i]==2 && i!=twopoint)
swap(nums[twopoint--],nums[i]);
else
i++;
}

}
};