19.2.13 [LeetCode 75] Sort Colors

Given an array with n objects colored red, white or blue, sort them in-place 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.

Example:

Input: [2,0,2,1,1,0]
Output: [0,0,1,1,2,2]

Follow up:

• A rather straight forward solution is a two-pass algorithm using counting sort.
  First, iterate the array counting number of 0's, 1's, and 2's, then overwrite array with total number of 0's, then 1's and followed by 2's.
• Could you come up with a one-pass algorithm using only constant space?

题意

给只包含0，1，2的数组排序

题解

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

感觉数算往年题看见过类似的题型，还是挺有趣的

虽然我还是WA了好几遍过的

狂赌之渊啥时候出熟肉啊，为啥生肉播放还不流畅x