求助，定义了str数组但是编译失败了

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

int n,m,k;string f[10005];

string find(string x){
	if (f[x]==x)return x;
	return find(f[x]);
}

int main(){
	cin>>n>>m;
	for (int i=0;i<n;++i)cin>>f[i];
	for (int i=0;i<m;++i){
		string s,b;
		f[s]=find(b);
	}
	cin>>k;
	for (int i=0;i<k;++i){
		string s,b;
		cin>>s>>b;
		if (find(s)==find(b)){
			cout<<"Yes.";
		}
		else {
			cout<<"No.";
		}
		cout<<endl;
	}
	return 0;
}

这题是P2256