【LeetCode】C# 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.

把相同颜色（数字）整理到一起。
思路，利用交换保证数组中各元素个数不变更。然后遍历数组，把指针遇到的0，与前面代表0边界的指针交换。

public class Solution {    public void SortColors(int[] nums) {        int p1 = 0, p2 = nums.Length - 1, index = 0;        while (index <= p2) {            if (nums[index] == 0) {                nums[index] = nums[p1];                nums[p1] = 0;                p1++;            }            if (nums[index] == 2) {                nums[index] = nums[p2];                nums[p2] = 2;                p2--;                continue;            }            index++;        }    }}