1、题目描述

请实现一个函数，把字符串 s 中的每个空格替换成"%20"。示例 1：输入：s = "We are happy."
输出："We%20are%20happy."限制：0 <= s 的长度 <= 10000

2、C++

class Solution {
public:string replaceSpace(string s) {// 1. 不额外产生空间开销, 扩充源字符串 s// 2. 从后向前遍历, 时间复杂度 O(n)size_t s_length = s.length();size_t old_index = s_length;size_t space_count = 0;for (auto elem : s){if (elem == ' '){space_count++;}}s.resize(s_length + space_count * 2);size_t new_index = s.length();while (old_index >= 0 && new_index > old_index){if (s[old_index] == ' '){ s[new_index--] = '0';s[new_index--] = '2';s[new_index--] = '%';}else{s[new_index--] = s[old_index];}old_index--;}return s;}
};

3、Python

class Solution:def replaceSpace(self, s: str) -> str:return s.replace(' ', "%20")