题目：

解题思路：

        字符串拼接，先遍历复制从下标为 target 开始的 len - target 位字符，再遍历复制前 target位字符至末尾。

char* dynamicPassword(char* password, int target) {
    int len = strlen(password);
    // int num = 0;
    int i = 0;
    char* result = (char*) malloc(sizeof(char) * (len+1));
    for (; i+target < len; i++) {
        result[i] = password[i+target];
    }
    for (int j = 0; j < target; j++) {
        result[i] = password[j];
        i++;
    }
    result[i] = '\0';
    return result;
}