Poj--1330（LCA，tarjan）-优快云博客

2014-10-26 15:28:49

思路：在线 / 离线LCA。练模板的。

 1 /*************************************************************************
 2     > File Name: 1330.cpp
 3     > Author: Nature
 4     > Mail: 564374850@qq.com 
 5     > Created Time: Sat 25 Oct 2014 04:22:56 PM CST
 6 ************************************************************************/
 7 
 8 #include <cstdio>
 9 #include <cstring>
10 #include <cstdlib>
11 #include <cmath>
12 #include <vector>
13 #include <map>
14 #include <set>
15 #include <stack>
16 #include <queue>
17 #include <iostream>
18 #include <algorithm>
19 using namespace std;
20 #define lp (p << 1)
21 #define rp (p << 1|1)
22 #define getmid(l,r) (l + (r - l) / 2)
23 #define MP(a,b) make_pair(a,b)
24 typedef long long ll;
25 const int INF = 1 << 30;
26 const int maxn = 10010;
27 
28 int T,n,ans,qa,qb;
29 int first[maxn],next[maxn],ver[maxn],ecnt;
30 int f[maxn],vis[maxn],fa[maxn];
31 
32 void Init(){
33     memset(first,-1,sizeof(first));
34     memset(vis,0,sizeof(vis));
35     memset(f,0,sizeof(f));
36     ecnt = 0;
37 }
38 
39 void Add_edge(int u,int v){
40     next[++ecnt] = first[u];
41     ver[ecnt] = v;
42     first[u] = ecnt;
43 }
44 
45 int Find(int x){
46     return fa[x] == x ? x : fa[x] = Find(fa[x]);
47 }
48 
49 void Union(int u,int v){
50     int x = Find(u);
51     int y = Find(v);
52     if(x != y)
53         fa[y] = x;
54 }
55 
56 bool Tarjan(int p){
57     fa[p] = p;
58     for(int i = first[p]; i != -1; i = next[i]){
59         int v = ver[i];
60         if(Tarjan(v))
61             return true;
62         Union(p,v);
63     }
64     vis[p] = 1;
65     if(p == qa && vis[qb]){
66         ans = Find(qb);
67         return true;
68     }
69     if(p == qb && vis[qa]){
70         ans = Find(qa);
71         return true;
72     }
73     return false;
74 }
75 
76 int main(){
77     int a,b;
78     scanf("%d",&T);
79     while(T--){
80         scanf("%d",&n);
81         Init();
82         for(int i = 1; i < n; ++i){        
83             scanf("%d%d",&a,&b);
84             Add_edge(a,b);
85             f[b] = 1;
86         }
87         scanf("%d%d",&qa,&qb);
88         for(int i = 1; i <= n; ++i){
89             if(!f[i]){
90                 Tarjan(i);
91                 break;
92             }
93         }
94         printf("%d\n",ans);
95     }
96     return 0;
97 }