荷兰国旗问题/三色旗问题(Leetcode 75. Sort Colors)

最新推荐文章于 2023-02-02 21:15:58 发布

原创最新推荐文章于 2023-02-02 21:15:58 发布 · 1k 阅读

1 ·

CC 4.0 BY-SA版权

本文介绍了一种将数组中红、白、蓝三种颜色排序的算法，使用整数0、1、2分别代表红、白、蓝，并通过一次遍历实现原地排序。

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.

class Solution {
public:
    void sortColors(vector<int>& nums) {
        
        if(nums.empty())
            return;
        int start = 0;
        int current = start;
        int end = nums.size()-1;
        
        while(current<=end)
        {
           if(nums[current] == 0)
           {
               if(nums[start]!=nums[current])
               {
                    int temp = nums[start];
                    nums[start] = 0 ;
                    nums[current] = temp;
               }
               start++;
               current++;
               
           }else if(nums[current] == 1)
           {
               current++;
               
           }else{
               if(nums[current]!=nums[end])
               {
                   int temp = nums[end];
                   nums[end] = 2;
                   nums[current] = temp;
               }
               end --;
           }
        }
        
        return;
    }
};

注：nums[current] == 1时，start++, current++是因为前面已经排好序，nums[current] == 2， end --，后面没有排好序，还需要继续判断。