POJ1986(LCA应用:求两结点之间距离)

#include"cstdio"
#include"cstring"
#include"vector"
using namespace std;
typedef pair<int,int> P;
const int MAXN=100005;
int V,E;
vector<P> G[MAXN];
vector<P> que[MAXN];
int par[MAXN];
int fnd(int x)
{
    if(par[x]==x)
        return x;
    return par[x]=fnd(par[x]);
}
int vis[MAXN];
int ans[MAXN];
int d[MAXN];

void dfs(int u,int fa)
{
    par[u]=u;
    for(int i=0;i<que[u].size();i++)
    {
        P no=que[u][i];
        int v=no.first;
        if(vis[v])    ans[no.second]=d[u]+d[v]-2*d[fnd(v)];
    }
    vis[u]=1;
    for(int i=0;i<G[u].size();i++)
    {
        P now=G[u][i];
        if(now.first==fa)    continue;
        d[now.first]=d[u]+now.second;
        dfs(now.first,u);
        par[now.first]=u;
    }
}


int main()
{
    while(scanf("%d%d",&V,&E)!=EOF&&V)
    {
        for(int i=1;i<=V;i++)
        {
            G[i].clear();
            que[i].clear();
        }
        memset(vis,0,sizeof(vis));
        memset(ans,0,sizeof(ans));
        memset(d,0,sizeof(d));
        for(int i=0;i<E;i++)
        {
            int u,v,cost;
            scanf("%d %d %d %*c",&u,&v,&cost);
            G[u].push_back(P(v,cost));
            G[v].push_back(P(u,cost));
        }
        int Q;
        scanf("%d",&Q);
        for(int i=1;i<=Q;i++)
        {
            int u,v;
            scanf("%d%d",&u,&v);
            que[u].push_back(P(v,i));
            que[v].push_back(P(u,i));
        }
        dfs(1,-1);
        for(int i=1;i<=Q;i++)
        {
            printf("%d\n",ans[i]);
        }    
    }
    
    return 0;
}