75-Sort Colors

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.

分析

利用三个指针

i和j分别是01分界和12分界

实现

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

}
void swap(vector<int>& nums, int i, int j)
{
int tmp = nums[i];
nums[i] = nums[j];
nums[j] = tmp;
}
};