Least Common Ancestors

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <vector>
using namespace std;
struct node
{
	int f, s;
};
vector<node>imap[40005];
int deep[40005];
int dis[40005];
int fa[40005];
int ffa[40005];
bool vis[40005];
void dfs(int n,int s,int ff)
{
	vis[n] = true;
	for(int i=0;i<imap[n].size();i++)
	{
		if(vis[imap[n][i].f])		continue;
		deep[imap[n][i].f] = s;
		dis[imap[n][i].f] = dis[n]+imap[n][i].s;
		fa[imap[n][i].f] = n;
		ffa[imap[n][i].f] = ff;
		dfs(imap[n][i].f,s+1,ff);
	}
}

int lca(int x, int y)
{
	if(x==y)	return dis[x];
	if(deep[x]>=deep[y])	return lca(fa[x],y);
	else return lca(x,fa[y]);
}
int main()
{
	int t, n, m, c;
	int u, v, s, ans; 
	node cur;
	while(scanf("%d%d%d",&n,&m,&c)!=EOF)
	{
		memset(vis,false,sizeof(vis));
		memset(fa,0,sizeof(fa));
		memset(fa,false,sizeof(fa));
		memset(dis,0,sizeof(dis));
		memset(deep,false,sizeof(deep));	
		memset(imap,0,sizeof(imap));
		for(int i=0;i<m;i++)
		{
			scanf("%d%d%d",&u,&v,&s);
			cur.f = v;
			cur.s = s;
			imap[u].push_back(cur);
			cur.f = u;
			imap[v].push_back(cur);
		}
		for(int i=1;i<=n;i++)
		{
			if(vis[i])	continue;
			ffa[i] = i;
			dfs(i,1,i);
		}
		for(int i=0;i<c;i++)
		{
			scanf("%d%d",&u,&v);
			if(ffa[u]!=ffa[v])	printf("Not connected\n");
			else
			{
				ans = lca(u,v);
				printf("%d\n",dis[u]+dis[v]-2*ans);
			}		
		} 
		
	}
	return 0;
} 

来自HDU2847