牛客网-《剑指offer》-替换空格

题目：http://www.nowcoder.com/practice/4060ac7e3e404ad1a894ef3e17650423

C++

 class Solution {
 public:
     void replaceSpace(char *str,int len) {
         int cnt = ;
         for (int i = ; i < len; i++) {
             if (str[i] == ' ') cnt++;
         }
         int idx = len + cnt *  - ;
         for (int i = len - ; i >= ; i--) {
             if (str[i] == ' ') {
                 str[idx--] = '';
                 str[idx--] = '';
                 str[idx--] = '%';
             } else {
                 str[idx--] = str[i];
             }
         }
     }
 };