人類智慧-AGC052B

令一個點的權值為其到根的經過的邊的異或和

注意到可以將操作視為交換兩個點的權值

#include<bits/stdc++.h>
using namespace std;
#define i128 __int128
#define ll long long
#define ull unsigned long long
#define pii pair<int,int>
#define fi first
#define se second
#define lowbit(x) ((x)&(-x))
#define It set<int>::iterator
//#define ls (rt<<1)
//#define rs (rt<<1|1)
//#define mid (l+r>>1)
//#define lson tr[rt].ls
//#define rson tr[rt].rs
//#define ls1 tr[rt1].ls
//#define rs1 tr[rt1].rs
//#define ls2 tr[rt2].ls
//#define rs2 tr[rt2].rs
#define pb emplace_back
const int mod=998244353;
int ksm(int x,int y){
	int res=1;
	while(y){
		if(y&1)res=1LL*res*x%mod;
		x=1LL*x*x%mod;
		y>>=1;
	}
	return res;
}
int n,f[100005],g[100005];
struct edge{
	int v,w1,w2,nx;
}e[200005];
int cnt,hd[100005];
void add(int u,int v,int w1,int w2){
	e[++cnt]=edge{v,w1,w2,hd[u]};
	hd[u]=cnt;
}
void dfs(int u,int fa){
	for(int i=hd[u];i;i=e[i].nx){
		int v=e[i].v;if(v==fa)continue;
		f[v]=f[u]^e[i].w1;g[v]=g[u]^e[i].w2;
		dfs(v,u);
	}
}
int main(){
	scanf("%d",&n);
	for(int i=1;i<n;i++){
		int u,v,w1,w2;scanf("%d%d%d%d",&u,&v,&w1,&w2);
		add(u,v,w1,w2);add(v,u,w1,w2);
	}
	dfs(1,0);
	int w=0;
	for(int i=1;i<=n;i++)w^=f[i]^g[i];
	for(int i=1;i<=n;i++)f[i]^=w;
	sort(f+1,f+1+n);sort(g+1,g+1+n);
	for(int i=1;i<=n;i++)
		if(f[i]!=g[i])
			puts("NO"),exit(0);
	puts("YES");
    return 0;
}