c/c++ No.16 求字符串长度

#include <iostream>#include <cstring> using namespace std;  int main() {    char a[7] = "123456";    cout << strlen(a) << endl;    cout << strlen(a) - 6 << endl;    cout << strlen(a) - 7 << endl;    cout << (int)strlen(a) - 7 << endl;    cout << (unsigned int)strlen(a) - 7 << endl;    cout << (unsigned long long)strlen(a) - 7 << endl;    return 0;  }