为啥是wrong answer

Question

案例也通过了，找了几个C++代码（没学过C++）发现主体大差不差

Answer 1

参考如下：

int main() {
    
    char str[30], r, n;
    cin >> str >> r >> n;
    int i = 0;
    while(str[i] != '\0') {
        if (str[i] == r) {
            str[i] = n;
        }
        i++;
    }
    cout << str << endl;
    return 0;
}