为什么这道题用cin可以通过，换成getline就不行了呢？代码如下：

#include<bits/stdc++.h>
using namespace std;

int main()
{
	string s1, s2;
	cin >> s1 >> s2;
	//getline(cin, s1);
	//getline(cin, s2);
	if (s1.find(s2)!=s1.npos) cout << s2 << " is substring of " << s1 << endl;
	else if (s2.find(s1)!=s2.npos) cout << s1 << " is substring of " << s2 << endl;
	else cout << "No substring" << endl;
	return 0;
}