POJ - 1330 Nearest Common Ancestors 最近公共祖先+链式前向星 模板题

  1 #include<cstdio>
  2 #include<cstdlib>
  3 #include<cstring>
  4 #include<cmath>
  5 #include<algorithm>
  6 #include<queue>
  7 #include<stack>
  8 #include<deque>
  9 #include<map>
 10 #include<iostream>
 11 using namespace std;
 12 typedef long long  LL;
 13 const double pi=acos(-1.0);
 14 const double e=exp(1);
 15 const int N = 10100;
 16 
 17 #define lson i << 1,l,m
 18 #define rson i << 1 | 1,m + 1,r
 19 int cnt,ans;
 20 int a,b,n;
 21 int root;
 22 int head[N];
 23 int is_root[N];
 24 int father[N];
 25 int vis[N];
 26 
 27 struct edge
 28 {
 29     int to;
 30     int next;
 31 } edge[N];
 32 
 33 int seek(int ss)
 34 {
 35     int mid;
 36     int head=ss;
 37     while(ss!=father[ss])
 38         ss=father[ss];
 39 
 40     while(head!=ss)
 41     {
 42         mid=father[head];
 43         father[head]=ss;
 44         head=mid;
 45     }
 46     return ss;
 47 }
 48 
 49 void join(int xx,int yy)
 50 {
 51     int one=seek(xx);
 52     int two=seek(yy);
 53     if(one!=two)
 54         father[two]=one;  //注意把谁变成谁的上级
 55 }
 56 
 57 void add(int x,int y)
 58 {
 59     edge[cnt].to=y;
 60     edge[cnt].next=head[x];
 61     head[x]=cnt++;
 62 }
 63 
 64 void init()
 65 {
 66     int i,p,j;
 67     int x,y;
 68     cnt=0;
 69     memset(head,-1,sizeof(head));
 70     memset(is_root,0,sizeof(is_root));
 71     memset(vis,0,sizeof(vis));
 72     scanf("%d",&n);
 73     for(i=0; i<=n; i++)
 74         father[i]=i;
 75     for(i=1; i<n; i++)
 76     {
 77         scanf("%d%d",&x,&y);
 78         add(x,y);
 79         is_root[y]=1;
 80     }
 81     for(i=1; i<=n; i++)
 82         if(is_root[i]==0)
 83             root=i;
 84 }
 85 
 86 void LCA(int u)
 87 {
 88     int i,p,j;
 89     for(i=head[u]; i!=-1; i=edge[i].next)
 90     {
 91         int v=edge[i].to;
 92         LCA(v);
 93         join(u,v);
 94         vis[v]=1;
 95     }
 96 
 97     if(u==a&&vis[b]==1)
 98         ans=seek(b);
 99     if(u==b&&vis[a]==1)
100         ans=seek(a);
101 
102     return ;
103 }
104 
105 void solve()
106 {
107     scanf("%d%d",&a,&b);
108     LCA(root);
109 }
110 
111 int main()
112 {
113     int t,m,i,p,j;
114     scanf("%d",&t);
115     for(i=1; i<=t; i++)
116     {
117         init();
118         solve();
119 
120         printf("%d\n",ans);
121     }
122     return 0;
123 }