poj1330

来源：互联网发布：淘宝搜索优化软件编辑：程序博客网时间：2024/06/05 17:53
LCA
#include<stdio.h>#include<string.h>#include<vector>#include<cmath>using namespace std;vector<int> c[10005];int n,cnt,first[10005],dfs_val[20100],dfs_deep[20100];int dp[20100][16];void dfs(int root,int deep){    dfs_deep[++cnt]=deep;    dfs_val[cnt]=root;    first[root]=cnt;    for(int i=0;i<c[root].size();i++)    {        dfs(c[root][i],deep+1);        dfs_deep[++cnt]=deep;        dfs_val[cnt]=root;    }}void st(){    int i,j;    for(i=1;i<=cnt;i++) dp[i][0]=i;    for(j=1;j<=(int)(log(1.0*cnt)/log(2.0));j++)    {        for(i=1;i<=cnt+1-(1<<j);i++)        {            int p=i+(1<<(j-1));            if(dfs_deep[dp[i][j-1]]>dfs_deep[dp[p][j-1]]) dp[i][j]=dp[p][j-1];            else dp[i][j]=dp[i][j-1];        }    }}int rmq(int l,int r){    l=first[l],r=first[r];    if(l>r) swap(l,r);    int k=(int)(log(1.0*(r-l+1))/log(2.0));    if(dfs_deep[dp[l][k]]<dfs_deep[dp[r+1-(1<<k)][k]]) return dp[l][k];    else return dp[r+1-(1<<k)][k];}int main(){    int i,t,x,y,root;    scanf("%d",&t);    while(t--)    {        scanf("%d",&n);        for(i=1;i<=n;i++) c[i].clear();        scanf("%d%d",&x,&y);        c[x].push_back(y);        root=x;        for(i=2;i<n;i++)        {            scanf("%d%d",&x,&y);            c[x].push_back(y);            if(y==root) root=x;        }        cnt=0;        memset(first,0,sizeof(first));        dfs(root,0);        st();        scanf("%d%d",&x,&y);        printf("%d\n",dfs_val[rmq(x,y)]);    }}
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