HDU2586 离线tarjan LCA

离线LCA求一棵树上的两点间的最近距离

#include <iostream>
#include <vector>
#include <cstdio>
#include <cstring>
#define maxn 41111
using namespace std;
struct node{
    int v,next,len;
}edge[84444];

struct que{
    int u,v,next,id;
}ask[422];
int father[maxn],vis[maxn],ans[maxn],in[maxn],lca[222];
int head[44444],h[44444],dis[44444];
int n,m,c,e,q;

void addedge(int u,int v,int w){
    edge[e].v = v;
    edge[e].len = w;
    edge[e].next = head[u];
    head[u] = e++;
}

void addquery(int u,int v,int w){
    ask[q].v = v;
    ask[q].u = u;
    ask[q].id = w;
    ask[q].next = h[u];
    h[u] = q++;
}
void init(){
    for(int i = 0 ; i <= n ; i ++){
        father[i] = i;
        vis[i] = 0;
        dis[i] = 0;
    }
    memset(head,-1,sizeof(head));
    memset(h,-1,sizeof(h));
    e = 0;
    q = 0;
}

int find(int x){
    if(father[x] == x)
        return x;
    int t = find(father[x]);
    father[x] = t;
    return t;
}

void LCA(int u){
    father[u] = u;
    vis[u] = 1;
    for(int i = h[u] ; i != -1 ; i = ask[i].next){
        int v = ask[i].v;
        if(vis[v] == 1){
            int root = find(v);
            lca[ask[i].id] = root;
        }
    }
    for(int i = head[u] ; i != -1 ; i = edge[i].next){
        int v = edge[i].v;
        if(!vis[v]){
            dis[v] = dis[u] + edge[i].len;
            LCA(v);
            father[v] = u;
        }
    }
}
int main()
{
    int T;
    scanf("%d",&T);
    while(T--){
        scanf("%d%d",&n,&m);
        init();
        for(int i = 1 ; i < n ; i++){
            int u,v,w;
            scanf("%d%d%d",&u,&v,&w);
            addedge(u,v,w);
            addedge(v,u,w);
        }
        for(int i = 0 ; i < m ; i ++){
            int a,b;
            scanf("%d%d",&a,&b);
            addquery(a,b,i);
            addquery(b,a,i);
        }
        LCA(1);
        for(int i = 0 ; i < q ; i += 2){
            printf("%d\n",dis[ask[i].u]+dis[ask[i].v]-2*dis[lca[ask[i].id]]);
        }
    }
    return 0;
}