有没有帮忙，找到问题了必关

#include<bits/stdc++.h>
using namespace std;
int n,m,k; 
struct shuzu{
	string mingzi;
	int bianhao;
};
shuzu a[20005];
int f(int x1,string x2){
	while(a[x1].mingzi!=x2) x2=a[x1].mingzi;
	return x1;
}
int c(string as){
	for(int i=1;i<=n;i++){
		if(a[i].mingzi==as) return a[i].bianhao;
	}
}
int main(){
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>a[i].mingzi;
		a[i].bianhao=i;
	}
	for(int i=1;i<=m;i++){
		string s1,s2;
		cin>>s1>>s2;
		int x=f(c(s1),s1),y=f(c(s2),s2);
		a[x].bianhao=y;
	}
	cin>>k;
	while(k--){
		string s3,s4;
		cin>>s3>>s4;
		int x=f(c(s3),s3),y=f(c(s4),s4);
		if(x==y) cout<<"Yes.";
		else cout<<"No.";
		cout<<endl;
	}
	return 0;
}

只得了40分，样例没过，求大佬帮助