POJ——T 1986 Distance Queries

 1 #include <algorithm>
 2 #include <cstdio>
 3 
 4 using namespace std;
 5 
 6 const int N(53333);
 7 char s[3];
 8 int n,m,dis[N],head[N],sumedge;
 9 struct Edge
10 {
11     int v,w,next;
12     Edge(int v=0,int next=0,int w=0):
13         v(v),next(next),w(w){}
14 }edge[N<<1];
15 inline void ins(int u,int v,int w)
16 {
17     edge[++sumedge]=Edge(v,head[u],w);
18     head[u]=sumedge;
19 }
20 
21 int size[N],top[N],dad[N],son[N],deep[N];
22 void DFS(int u,int fa,int deepth)
23 {
24     dad[u]=fa;
25     size[u]=1;
26     deep[u]=deepth;
27     for(register int v,i=head[u];i;i=edge[i].next)
28     {
29         v=edge[i].v;
30         if(dad[u]==v) continue;
31         dis[v]=dis[u]+edge[i].w;
32         DFS(v,u,deepth+1);
33         size[u]+=size[v];
34         if(size[son[u]]<size[v]) son[u]=v;
35     }
36 }
37 void DFS_(int u,int Top)
38 {
39     top[u]=Top;
40     if(son[u]) DFS_(son[u],Top);
41     for(int v,i=head[u];i;i=edge[i].next)
42     {
43         v=edge[i].v;
44         if(dad[u]!=v&&son[u]!=v) DFS_(v,v);
45     }
46 }
47 int LCA(int x,int y)
48 {
49     for(;top[x]!=top[y];x=dad[top[x]])
50         if(deep[top[x]]<deep[top[y]]) swap(x,y);
51     return deep[x]<deep[y]?x:y;
52 }
53 
54 int main()
55 {
56     scanf("%d%d",&n,&m);
57     for(int u,v,w;m--;)
58     {
59         scanf("%d%d%d%s",&u,&v,&w,s);
60         ins(u,v,w); ins(v,u,w);
61     }
62     DFS(1,0,1); DFS_(1,1);
63     int k;scanf("%d",&k);
64     for(int u,v;k--;)
65     {
66         scanf("%d%d",&u,&v);
67         printf("%d\n",dis[v]+dis[u]-dis[LCA(u,v)]*2);
68     }
69     return 0;
70 }