POJ 1330 Nearest Common Ancestors LCA

来源：互联网发布：化妆品真伪查询软件编辑：程序博客网时间：2024/05/16 05:22

给一棵树，查询两个点的最近公共祖先。还是模板题，不过数据给的时候是按顺序给的，所以要直接存成从根节点到叶子节点的有向图，同时存一下每个点的入度用来找根节点，然后从根节点开始做一遍tarjan就行..

#include <iostream>#include <cstdio>#include <algorithm>#include <memory.h>#include <cmath>using namespace std;typedef long long ll;const int maxn=40000+40;struct node{    int w,v;    int next;}edge[maxn<<1],query[500];bool vis[maxn];int g[maxn],gg[maxn];int res[maxn][3];int m,n,k,p,q;int en,eq;int test;int fa[maxn];int dis[maxn];int find(int x){    if (x!=fa[x]) return fa[x]=find(fa[x]);    return x;}void tarjan(int u){    vis[u]=true;    fa[u]=u;    for (int j=gg[u]; j!=-1; j=query[j].next)    {        if (vis[query[j].v])        {            res[query[j].w][2]=find(query[j].v);        }    }    for (int j=g[u]; j!=-1; j=edge[j].next)    {        if (!vis[edge[j].v])        {            dis[edge[j].v]=dis[u]+edge[j].w;            tarjan(edge[j].v);            fa[edge[j].v]=u;        }    }}int ideg[maxn];int main(){//    freopen("in.txt","r",stdin);    scanf("%d",&test);    while (test--)    {        memset(vis,false,sizeof vis);        memset(dis,0,sizeof dis);        memset(ideg,0,sizeof ideg);        scanf("%d",&n);//        scanf("%d",&m);        m=1;        memset(g,-1,sizeof g);        memset(gg,-1,sizeof gg);        en=eq=0;        int x,y,z;        int root=-1;        for (int i=1; i<n; i++)        {            scanf("%d%d",&x,&y);            ideg[y]++;            if (root==-1) root=x;            z=1;            edge[en].w=z;            edge[en].v=y;            edge[en].next=g[x];            g[x]=en;            en++;        }        for (int i=1; i<=m; i++)        {            scanf("%d%d",&x,&y);            query[eq].v=y;            query[eq].w=i;            query[eq].next=gg[x];            gg[x]=eq;            eq++;            query[eq].v=x;            query[eq].w=i;            query[eq].next=gg[y];            gg[y]=eq;            eq++;            res[i][0]=x;            res[i][1]=y;        }        for (int i=1; i<=n; i++)        if (ideg[i]==0)        {            root=i;            break;        }        dis[root]=0;        tarjan(root);        cout<<res[1][2]<<endl;    }    return 0;}

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