[剑指offer 编程题]替换空格

class Solution {
public:
    void replaceSpace(char *str,int length) {
        string str_2 = "";
        int plus_length = 0;

         for(int i = 0;i<length;i++){
            if(str[i] != ' '){
                str_2 += str[i];
            }
            else {
                str_2 += "%20";
                plus_length += 2;
            }
         }  
        length += plus_length;

         for(int j = 0;j<length;j++){
             str[j] = str_2[j];            
         }

    }
};