C++-hihoCode1545-小Hi和小Ho的对弈游戏[树上Nim]

 #include <set>
 #include <map>
 #include <cmath>
 #include <queue>
 #include <vector>
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
 #include <iostream>
 #include <algorithm>
 using namespace std;
 const int MAXN=,MAXM=;
 struct edge{
     int v,next;
     edge(int v=,int next=):v(v),next(next){}
 };

 edge E[MAXM];int head[MAXN],cnt,d[MAXN],sg[MAXN],g,rt;
 void add(int u,int v){E[++cnt]=edge(v,head[u]),head[u]=cnt;}

 void init(){
     cnt=g=;
     memset(d,,sizeof(d));
     memset(head,,sizeof(head));
 }

 void dfs(int u,int fa){
     sg[u]=;
     for(int i=head[u];i;i=E[i].next)
         if(E[i].v!=fa)
             dfs(E[i].v,u);
     sg[fa]^=(sg[u]+);
     if(fa==rt)g^=sg[u];
 }

 int main(){
     int q,n;
     for(scanf("%d",&q);q--;){
         init(),scanf("%d",&n);
         for(int i=,u,v; i<n; i++)scanf("%d%d",&u,&v),add(u,v),d[v]++;
         for(int i=;i<=n;i++)if(!d[i])rt=i;//注意题目的隐含意思是加入的单项边
         dfs(rt,);
         putchar(sg[rt]?'':'');
         putchar(g?'':'');
     }
     return ;
 }