吝啬的国度

就是暴力搜索即可
dfs+链式前向星

题目链接<-点击

#include<cmath>#include<iostream>#include<cstdio>#include<cstring>using namespace std;int pre[100005],head[100005];int cnt=0;struct edge{    int v,next;}edge[100005*2];void add_edge(int u,int v){    edge[cnt].v=v;    edge[cnt].next=head[u];    head[u]=cnt++;}void dfs(int s){    for(int i=head[s];i!=-1;i=edge[i].next)    {        int to=edge[i].v;        if(pre[to])            continue;        pre[to]=s;        dfs(to);    }}int main (){    int t;    cin>>t;    while(t--)    {        int n,m;        cin>>n>>m;        int i;        cnt=0;        memset(head,-1,sizeof(head));        memset(pre,0,sizeof(pre));        pre[m]=-1;        for(i=1;i<n;i++)        {            int a,b;            scanf("%d%d",&a,&b);            add_edge(a,b);            add_edge(b,a);        }        dfs(m);        for(i=1;i<n;i++)        {            printf("%d ",pre[i]);        }        printf("%d\n",pre[n]);    }}