LCA模板

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <stdio.h>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <iomanip>
#include <list>
#include <deque>
#include <stack>
#define ull unsigned long long
#define ll long long
#define mod 90001
#define INF 0x3f3f3f3f
#define maxn 40000+10
#define cle(a) memset(a,0,sizeof(a))
const ull inf = 1LL << 61;
const double eps=1e-5;
using namespace std;

bool cmp(int a,int b){
    return a>b;
}
int fa[maxn],n,m,pre[maxn],l;
int lca[1000][1000];

struct node{
    int v,next;
}edge[maxn+100];
void add(int u,int v){
    edge[l].v=v;
    edge[l].next=pre[u];
    pre[u]=l++;
}
int findfa(int x){
    if(x==fa[x])return x;
    else return fa[x]=findfa(fa[x]);
}
void Union(int x,int y){
    x=findfa(x);
    y=findfa(y);
    fa[y]=x;
}
void dfs(int u){
   int  v;
   fa[u]=u;
   for(int i=pre[u];i+1;i=edge[i].next){
        v=edge[i].v;
        if(fa[v]==-1){
            dfs(v);
            Union(u,v);
        }
    }
	for(v=1;v<=n;v++){
		if(fa[v]!=-1){
			lca[u][v]=lca[v][u]=findfa(v);
		}
	}
}
int main()
{
    #ifndef ONLINE_JUDGE
    freopen("in.txt","r",stdin);
    #endif
    //freopen("out.txt","w",stdout);
    int t;
    cin>>t;
    int x,y,k;
    while(t--){
        scanf("%d%d%d",&n,&m,&k);
        l=0;
        memset(fa,-1,sizeof fa);
        memset(pre,-1,sizeof pre);
        for(int i=1;i<=m;i++){
            cin>>x>>y;
            add(x,y);
            add(y,x);
        }
        dfs(1);
		for(int i=1;i<=k;i++){
			cin>>x>>y;
			cout<<lca[x][y]<<endl;
		}
    }
    return 0;
}