调用库函数

#include<bits/stdc++.h>
#define ll long long                                                                                            //防伪标识
#define MAXN 1005
#define maxn 10005
#define MAXM 10000
#define maxm 1000005
using namespace std;
string a;
string b;
string::size_type idx;
string::size_type n;
int main(){
	cin >> b;
	cin>>a;
	idx=a.find(b);
	n = b.find(a);
	if(idx == string::npos &&n == string::npos)
		cout << "No substring";
	else if(idx == string::npos)
        cout <<a<<" is substring of "<<b;
	else 
        cout <<b<<" is substring of "<<a;
	return 0;
}