HDU2586

#include<iostream>#include<cstring>#include<cstdio>#include<cmath>#include<algorithm>using namespace std;#define MAXN 40040int head[MAXN],tot,dis[MAXN],n,m;struct Edge{ int value,to,next; }e[MAXN<<2];int dep[MAXN],son[MAXN],siz[MAXN],fa[MAXN],top[MAXN];inline void prepare(){    memset(dis,0,sizeof dis ); tot=0;    memset(head,0,sizeof head );    memset(son,0,sizeof son );    memset(dep,0,sizeof dep );    memset(fa,0,sizeof fa );}inline int read(int &x){    x=0; int f=1; char c=getchar();    while(c>'9'||c<'0'){ if(c=='-') f=-1; c=getchar(); }    while(c>='0'&&c<='9'){ x=x*10+c-'0'; c=getchar(); } x*=f;}inline void Add_Edge(int u,int v,int w){    e[++tot].to=v; e[tot].value=w;    e[tot].next=head[u]; head[u]=tot;}void DFS_1(int u,int father,int deepth){    dep[u]=deepth,siz[u]=1,fa[u]=father;    for(int i=head[u];i;i=e[i].next){        int v=e[i].to;        if(v==father) continue;        dis[v]=e[i].value+dis[u];        DFS_1(v,u,deepth+1);        siz[u]+=siz[v];        if(!son[u]||siz[son[u]]<siz[v]) son[u]=v;    }}void DFS_2(int u,int Top){    top[u]=Top;    if(son[u]) DFS_2(son[u],Top);    for(int i=head[u];i;i=e[i].next){        int v=e[i].to;        if(v==fa[u]||v==son[u]) continue;        DFS_2(v,v);    }}inline int Get_LCA(int u,int v){    while(top[u]!=top[v]){        if(dep[top[u]]<dep[top[v]]) swap(u,v);        u=fa[top[u]];    }    if(dep[u]>dep[v]) swap(u,v);    return u;}int main(){    int T; read(T);    while(T--){        prepare();        read(n),read(m);        for(int u,v,w,i=1;i<=n-1;++i){            read(u),read(v),read(w);            Add_Edge(u,v,w);Add_Edge(v,u,w);        }        DFS_1(1,0,1); DFS_2(1,1);        for(int u,v,i=1;i<=m;++i){            read(u),read(v);            int lca=Get_LCA(u,v);            printf("%d\n",dis[u]+dis[v]-dis[lca]-dis[lca]);        }    }    return 0;}