替换空格

题目描述

请实现一个函数，将一个字符串中的空格替换成“%20”。例如，当字符串为We Are Happy.则经过替换之后的字符串为We%20Are%20Happy。

思路
从后往前替换

class Solution {public:    void replaceSpace(char *str,int length) {        int i = length-1;        while(i >= 0) {            if((int)str[i] == 32) {                length += 2;                int j = length-1;                while(j > i+2) {                    str[j] = str[j-2];                    j--;                }                str[i] = '%';                str[i+1] = '2';                str[i+2] = '0';            }            i--;        }    }};