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.

分析： 一开始看到这个觉得肯定有非常简单有效地算法，采用多指针法，注意w,r,b的顺序，还是比较难想的

class Solution {
public:
    void sortColors(vector<int>& nums) {
        int r = , w = , b = ;
        for (int i = ; i < nums.size(); i++) {
            int num = nums[i];
            cout << num << endl;
            if (num == ) {nums[b++] = ; nums[w++] = ; nums[r++] = ; }
            else if (num == ) {nums[b++] = ; nums[w++] = ;}
            else if (num == ) b++;
    }
    }
};