zoj 3195题目链接 题意：求树上三点的最短距离。。。 思路：两两求，和除以2. 因为忘记初始化p=0..WA了将近两个小时。。。？ 妈的智障。
代码实现
1/* ***********************************************
2Author :111qqz
3Created Time :2016年05月21日 星期六 14时44分39秒
4File Name :code/zoj/3195.cpp
5************************************************ */
6
7
8
9#include <cstdio>
10#include <cstring>
11#include <iostream>
12#include <algorithm>
13#include <vector>
14#include <queue>
15#include <set>
16#include <map>
17#include <string>
18#include <cmath>
19#include <cstdlib>
20#include <ctime>
21#define fst first
22#define sec second
23#define lson l,m,rt<<1
24#define rson m+1,r,rt<<1|1
25#define ms(a,x) memset(a,x,sizeof(a))
26typedef long long LL;
27#define pi pair < int ,int >
28#define MP make_pair
29
30using namespace std;
31const double eps = 1E-8;
32const int dx4[4]={1,0,0,-1};
33const int dy4[4]={0,-1,1,0};
34const int inf = 0x3f3f3f3f;
35const int N=5E4+7;
36int n,m;
37vector < pi > edge[N];
38int q;
39int in[N];
40int E[2*N],R[2*N],dis[N],depth[2*N];
41int p;
42int dp[2*N][20];
43void dfs( int u,int dep,int d,int pre)
44{
45
46 // cout<<"u:"<<u<<" dep:"<<dep<<" d:"<<d<<endl;
47 p++;
48 E[p] = u;
49 depth[p] = dep;
50 R[u] = p ;
51 dis[u] = d;
52
53
54 int siz = edge[u].size();
55 for ( int i = 0 ; i < siz ; i++)
56 {
57 int v = edge[u][i].fst;
58 if (v==pre) continue;
59 dfs(v,dep+1,d+edge[u][i].sec,u);
60
61 p++;
62 E[p] = u;
63 depth[p] = dep;
64 }
65}
66
67
68
69int _min( int l,int r)
70{
71 if (depth[l]<depth[r]) return l;
72 return r;
73}
74void rmq_init()
75{
76 for ( int i = 1 ; i <= 2*n+2 ; i++) dp[i][0] = i;
77
78 for ( int j = 1 ; (1<<j) <= 2*n+2 ; j++)
79 for ( int i = 1 ; i + (1<<j)-1 <= 2*n+2 ; i++)
80 dp[i][j] = _min(dp[i][j-1],dp[i+(1<<(j-1))][j-1]);
81}
82
83int rmq_min( int l,int r)
84{
85 if (l>r) swap(l,r);
86 int k = 0 ;
87 while (1<<(k+1)<=r-l+1) k++;
88 return _min(dp[l][k],dp[r-(1<<k)+1][k]);
89}
90int solve (int x,int y)
91{
92 int LCA = E[rmq_min(R[x],R[y])];
93 int res = dis[x] + dis[y] - 2 * dis[LCA];
94 return res;
95}
96int main()
97{
98 #ifndef ONLINE_JUDGE
99 freopen("code/in.txt","r",stdin);
100 #endif
101
102 ms(in,0);
103 bool ok = false;
104 while (~scanf("%d",&n)){
105 if (ok) puts("");
106 ok = true;
107 for ( int i = 0 ; i <= n ; i++) edge[i].clear();
108 for ( int i = 1 ; i <= n-1 ; i++)
109 {
110 int u,v,w;
111 scanf("%d%d%d",&u,&v,&w);
112 edge[u].push_back(make_pair(v,w));
113 edge[v].push_back(make_pair(u,w));
114 }
115
116
117 p = 0 ;
118 dfs(0,0,0,-1);
119 rmq_init();
120
121 scanf("%d",&q);
122 while (q--)
123 {
124 int x,y,z;
125 scanf("%d%d%d",&x,&y,&z);
126 int ans = solve(x,y)+solve(x,z)+solve(y,z);
127 printf("%d\n",ans/2);
128 }
129 }
130
131#ifndef ONLINE_JUDGE
132 fclose(stdin);
133#endif
134 return 0;
135}