POJ 1986 Distance Queries 【输入YY && LCA（Tarjan离线）】

 1 #include <cstdio>
 2 #include <iostream>
 3 #include <algorithm>
 4 #include <vector>
 5 #include <cstring>
 6 #define INF 0x3f3f3f3f
 7 #define LL long long
 8 using namespace std;
 9 const int MAXN = 5e5+5;
10 struct Edge{int v, w, nxt;}edge[MAXN<<1];
11 struct Query
12 {
13     int v, id;
14     Query(){};
15     Query(int _v, int _id):v(_v),id(_id){};
16 };
17 vector<Query> q[MAXN];
18 
19 int head[MAXN], cnt;
20 int dis[MAXN];
21 int fa[MAXN];
22 bool vis[MAXN];
23 int ans[MAXN];
24 int N, M, K;
25 
26 void init()
27 {
28     memset(vis, false, sizeof(vis));
29     memset(head, -1, sizeof(head));
30     memset(dis, 0, sizeof(dis));
31     memset(ans, 0, sizeof(ans));
32     for(int i = 0; i <= N; i++) q[i].clear();
33     cnt = 0;
34 }
35 
36 int getfa(int x){return fa[x]==x?x:fa[x]=getfa(fa[x]);}
37 
38 void AddEdge(int from, int to, int weight)
39 {
40     edge[cnt].v = to;
41     edge[cnt].w = weight;
42     edge[cnt].nxt = head[from];
43     head[from] = cnt++;
44 }
45 
46 void dfs(int s, int f)
47 {
48     int root = s;
49     for(int i = head[s]; i != -1; i = edge[i].nxt){
50         if(edge[i].v == f) continue;
51         dis[edge[i].v] = dis[root] + edge[i].w;
52         dfs(edge[i].v, s);
53     }
54 }
55 
56 void Tarjan(int s, int f)
57 {
58     int root = s;
59     fa[s] = s;
60     for(int i = head[s]; i != -1; i = edge[i].nxt){
61         int Eiv = edge[i].v;
62         if(Eiv == f) continue;
63         Tarjan(Eiv, root);
64         fa[getfa(Eiv)] = root;
65     }
66     vis[s] = true;
67     for(int i = 0; i < q[s].size(); i++){
68         if(vis[q[s][i].v] && ans[q[s][i].id] == 0){
69             ans[q[s][i].id] = dis[q[s][i].v] + dis[s] - 2*dis[getfa(q[s][i].v)];
70         }
71     }
72 }
73 
74 int main()
75 {
76     scanf("%d%d", &N, &M);
77     init();
78     char s;
79     for(int i = 1, u, v, w; i <= M; i++){
80         scanf("%d%d%d %c", &u, &v, &w, &s);
81         AddEdge(u, v, w);
82         AddEdge(v, u, w);
83     }
84     scanf("%d", &K);
85     for(int i = 1, u, v; i <= K; i++){
86         scanf("%d%d", &u, &v);
87         q[u].push_back(Query(v, i));
88         q[v].push_back(Query(u, i));
89     }
90     dfs(1, -1);
91     Tarjan(1, -1);
92     for(int i = 1; i <= K; i++){
93         printf("%d\n", ans[i]);
94     }
95     return 0;
96 }