3 XXX YYY ZZZ 2 XXX YYY YYY ZZZ 0
2
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <queue>
#include <algorithm>
#include <map>
#include <cmath>
#include <iomanip>
#define INF 99999999
typedef long long LL;
using namespace std;
const int MAX=1000+10;
int n,m,size,index,sum;
int head[MAX],dist[MAX];
int num[MAX];
map<string,int>mp;
struct Edge{
int v,next;
Edge(){}
Edge(int V,int NEXT):v(V),next(NEXT){}
}edge[MAX*20];
void Init(int num){
memset(head,-1,sizeof head);
size=sum=0;
}
void InsertEdge(int u,int v){
edge[size]=Edge(v,head[u]);
head[u]=size++;
}
void BFS(int u){
queue<int>q;
q.push(u);
for(int i=0;i<=n;++i)dist[i]=INF;
dist[u]=1;
while(!q.empty()){
u=q.front();
q.pop();
for(int i=head[u];i != -1;i=edge[i].next){
int v=edge[i].v,d=dist[u]+1;
if(d>=dist[v])continue;
dist[v]=d;
q.push(v);
if(dist[v]>sum)sum=dist[v],index=v;
if(dist[v] == sum && num[v]<num[index])index=v;
}
}
}
int main(){
char name[12],name2[12];
int u,v;
while(scanf("%d",&n),n){
memset(num,0,sizeof num);
mp.clear();
Init(n);
int k=0;
for(int i=0;i<n;++i){
scanf("%s",name);
mp[name]=++k;
}
cin>>m;
for(int i=0;i<m;++i){
scanf("%s%s",name,name2);
u=mp[name];
v=mp[name2];
InsertEdge(u,v);
InsertEdge(v,u);
++num[u];
++num[v];
}
index=1;
//for(int i=1;i<=n;++i)
BFS(1);
BFS(index);
for(int i=1;i<=n;++i)if(dist[i] == INF)sum=0;
cout<<sum-1<<endl;
}
return 0;
}
原文：http://blog.csdn.net/xingyeyongheng/article/details/25735377