牛客网-《剑指offer》-替换空格

class Solution {
public:
void replaceSpace(char *str,int len) {
int cnt = 0;
for (int i = 0; i < len; i++) {
if (str[i] == ' ') cnt++;
}
int idx = len + cnt * 2 - 1;
for (int i = len - 1; i >= 0; i--) {
if (str[i] == ' ') {
str[idx--] = '0';
str[idx--] = '2';
str[idx--] = '%';
} else {
str[idx--] = str[i];
}
}
}
};