POJ 1330:nearest Common Ancestors "LCA"

The question is: Well, give you a tree and two points and ask you what the LCA of these two points is

Idea: The template problem of LCA, it is important to note that when merging with the collection is not random, but the leaf node to the parent node

#include <cstdio>

#include <string.h>

#include <iostream>

#include <algorithm>

#include <math.h>

#define MAXN 10002

#define MOD 1000000007

using namespace Std;

int HEAD[MAXN],POINT[MAXN],NEXT[MAXN],FATHER[MAXN];

int now=0,in[maxn],finish=0;

BOOL VISIT[MAXN];

inline int Read ()

{

int X=0;char Ch=getchar ();

while (ch< ' 0 ' | | Ch> ' 9 ') Ch=getchar ();

while (ch>= ' 0 ' &&ch<= ' 9 ') {x=x*10+ch-' 0 '; Ch=getchar ();}

return x;

}

void Add (int x,int y)

{

NEXT[++NOW]=HEAD[X];

Head[x]=now;

Point[now]=y;

}

int find (int x)

{

if (X==father[x]) return x;

Return Father[x]=find (Father[x]);

}

void Dfs (int k,int s,int t)

{

for (int i=head[k];i;i=next[i])

{

if (finish==1) return;

int u=point[i];

DFS (U,S,T);

int X=find (k), Y=find (U);

if (x!=y) father[y]=x;

}

Visit[k]=1;

if (k==s && visit[t]) {printf ("%d\n", find (t)); finish=1;}

else if (k==t && visit[s]) {printf ("%d\n", find (s)); finish=1;}

return;

}

int main ()

{

int tt,n,x,y,root,s,t;

scanf ("%d", &TT);

while (tt--)

{

now=finish=0;

N=read ();

for (int i=1;i<=n;i++) father[i]=i;

for (int i=1;i<n;i++)

{

X=read (), Y=read ();

Add (x, y);

in[y]++;

}

for (int i=1;i<=n;i++) if (in[i]==0) Root=i;else in[i]=0;

S=read (), T=read ();

DFS (ROOT,S,T);

int u=sizeof (int) * (n+3);

int v=sizeof (BOOL) * (N+3);

memset (VISIT,0,V);

memset (Head,0,u);

}

return 0;

}

POJ 1330:nearest Common Ancestors "LCA"