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[Leetcode]344. Reverse String(C++)

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:

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#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)