Leetcode: Sort Colors

最新推荐文章于 2025-08-08 11:49:43 发布

店小不2

最新推荐文章于 2025-08-08 11:49:43 发布

阅读量470

点赞数

CC 4.0 BY-SA版权

分类专栏： Leetcode 文章标签： leetcode

本文链接：https://blog.youkuaiyun.com/xiaoxixixiyang/article/details/39180767

Leetcode 专栏收录该内容

119 篇文章

订阅专栏

本文介绍了一种不使用排序库的颜色排序算法。该算法采用一过式方法，在常数空间内完成红、白、蓝三色的排序。通过遍历数组并使用头部和尾部指针进行元素交换实现。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

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.

click to show follow up.

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 an one-pass algorithm using only constant space?

思路：遍历数组元素，选取头尾位置变量，为0则和头位置的元素交换，为2则和尾位置的元素交换。

public class Solution {
    public void sortColors(int[] A) {
        if (A == null || A.length <= 1) {
            return;
        }
        
        int start = 0;
        int end = A.length - 1;
        int i = 0;
        while (i <= end) {
            if (A[i] == 0) {
                swap(A, i, start);
                start++;
                i++;
            } else if (A[i] == 2) {
                swap(A, i, end);
                end--;
            } else {
                i++;
            }
        }
    }
    
    private void swap(int[] A, int i, int j) {
        int temp = A[i];
        A[i] = A[j];
        A[j] = temp;
    }
}