Sort Colors (Leetcode 75)

这题考查 Three-Way Partition 要点是while loop条件是有等于号的

while(start <= right)

同时，了解一下Rainbow Sort的算法。

void sortColors(vector &nums) {
        // write your code here
        if(nums.empty()) return;
        int left = 0, right = nums.size()-1;
        int start = 0;
        while(start <= right){
            if(nums[start] == 0){
                swap(nums[left], nums[start]);
                left++; start++;
            }else if(nums[start] == 2){
                swap(nums[start], nums[right]);
                right--;
            }else{
                start++;
            }
        }
    }