题目描述

题目链接：344. Reverse String

Write a function that reverses a string. The input string is given as an array of characters char[].

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

You may assume all the characters consist of printable ascii characters.

例子

例子 1

Input: [“h”,“e”,“l”,“l”,“o”] Output: [“o”,“l”,“l”,“e”,“h”]

例子 2

Input: [“H”,“a”,“n”,“n”,“a”,“h”] Output: [“h”,“a”,“n”,“n”,“a”,“H”]

解题思路

前后双指针，一个指针指向数组头，另一个指针指向数组尾部，分别往后/前遍历，依次交换字符即可，代码如下：

#include <vector>

class Solution {
public:
    void reverseString(std::vector<char>& s) {
        int front = 0, back = s.size() - 1;
        while (front < back) {
            std::swap(s[front], s[back]);
            front++;
            back--;
        }
    }
};

• 时间复杂度: O(n)
• 空间复杂度: O(1)