bsoj1375 tarjan离线求lca

来源：互联网发布：魔法王座升阶数据大全编辑：程序博客网时间：2024/06/06 04:54

模板题。。。不多说了很好理解

#include<iostream>#include<cstring>#include<cstdio>#include<algorithm>#define MAX 200005#define rep(i,j,k) for(int i=j;i<=k;i++)using namespace std;int n,k,to[2*MAX],next[2*MAX],head[MAX],ask_to[2*MAX],ask_next[2*MAX],ask_head[MAX];int tot=0,Tot=0;int num[MAX*2],father[MAX],ans[MAX],done[MAX],mark[MAX],root,m;void add(int from,int To){to[++tot]=To;next[tot]=head[from];head[from]=tot;}void add_ask(int from,int To,int Num){ask_to[++Tot]=To;num[Tot]=Num;ask_next[Tot]=ask_head[from];ask_head[from]=Tot;}int getfather(int x){if(father[x]==x)return x;father[x]=getfather(father[x]);return father[x];}void tarjan(int x){done[x]=1;father[x]=x;for(int i=head[x];i;i=next[i]){int y=to[i];if(!done[y]){tarjan(y);father[y]=x;}}mark[x]=1;for(int i=ask_head[x];i;i=ask_next[i]){int y=ask_to[i];if(mark[y])ans[num[i]]=getfather(y);}}int main(){scanf("%d%d",&n,&m);rep(i,1,n-1){int a1,a2;scanf("%d%d",&a1,&a2);add(a1,a2);father[a2]=a1;}rep(i,1,m){int a1,a2;scanf("%d%d",&a1,&a2);add_ask(a1,a2,i);add_ask(a2,a1,i);}root=1;while(father[root])root=father[root];tarjan(root);rep(i,1,m)printf("%d\n",ans[i]);return 0;}

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