HDU-2586-裸LCA入门-tarjan离线

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<map>
 5 #include<set>
 6 #include<stack>
 7 #include<deque>
 8 #include<bitset>
 9 #include<unordered_map>
10 #include<unordered_set>
11 #include<queue>
12 #include<cstdlib>
13 #include<ctype.h>
14 #include<ctime>
15 #include<functional>
16 #include<algorithm>
17 #include<bits/stdc++.h>
18 using namespace std;
19 #define LL long long 
20 #define pii pair<int,int>
21 #define mp make_pair
22 #define pb push_back
23 #define fi first
24 #define se second
25 #define inf 0x3f3f3f3f
26 #define debug puts("debug")
27 #define mid ((L+R)>>1)
28 #define lc (id<<1)
29 #define rc (id<<1|1)
30 const int maxn=40010;
31 const int maxm=50050;
32 const double PI=acos(-1.0);
33 const double eps=1e-6;
34 const LL mod=1e9+7;
35 LL gcd(LL a,LL b){return b==0?a:gcd(b,a%b);}
36 LL lcm(LL a,LL b){return a/gcd(a,b)*b;}
37 LL qpow(LL a,LL b,LL c){LL r=1; for(;b;b>>=1,a=a*a%c)if(b&1)r=r*a%c;return r;}
38 template<class T>
39 void prt(T v){for(auto x:v)cout<<x<<‘ ‘;cout<<endl;}
40 struct Edge{int u,v,w,next;};
41 
42 vector<pii>g[maxn],q[maxn];
43 int d[maxn],f[maxn],qu[220],qv[220],ans[220];
44 bool vis[maxn];
45 int getf(int u){return f[u]==u?u:f[u]=getf(f[u]);}
46 void tarjan(int u){
47     vis[u]=1;
48     for(pii e:g[u]){
49         int v=e.fi,w=e.se;
50         if(!vis[v]){
51             d[v]=d[u]+w;
52             tarjan(v);
53             f[v]=u;
54         }
55     }
56     for(pii e:q[u]){
57         int v=e.fi,id=e.se;
58         if(vis[v]){
59             ans[id]=getf(v);
60         }
61     }
62 }
63 int main(){
64     int t,n,m,i,j,u,v,w;
65     scanf("%d",&t);
66     while(t--){
67         scanf("%d%d",&n,&m);
68         for(i=1;i<=n;++i){
69             g[i].clear();
70             q[i].clear();
71             f[i]=i;
72             vis[i]=0;
73         }
74         for(i=1;i<n;++i){
75             scanf("%d%d%d",&u,&v,&w);
76             g[u].pb(mp(v,w));
77             g[v].pb(mp(u,w));
78         }
79         for(i=1;i<=m;++i){
80             scanf("%d%d",qu+i,qv+i);
81             q[qu[i]].pb(mp(qv[i],i));
82             q[qv[i]].pb(mp(qu[i],i));
83         }
84         tarjan(1);
85         for(i=1;i<=m;++i){
86             printf("%d\n",d[qu[i]]+d[qv[i]]-2*d[ans[i]]);
87         }
88     }
89     return 0;
90 }