树同构 树哈希

P5043 【模板】树同构（[BJOI2015]树的同构）

树哈希的板子，判断两个树是否有一种形态是相同的

#include <bits/stdc++.h>
#define inf 0x7fffffff
#define ll long long
//#define int long long
//#define double long double
#define re register int
#define void inline void
#define eps 1e-18
//#define mod 1e9+7
#define ls(p) p<<1
#define rs(p) p<<1|1
//#define ls(p) e[p].l
//#define rs(p) e[p].r
//#define pi acos(-1.0)
#define pb push_back
//#define P pair < int , int >
#define mk make_pair
#define fi first
#define se second
using namespace std;
const int mod=998244353;
const int M=1e8+5;
const int N=1e3+1;//?????????? 4e8.
ll ans[N][N];
int n,m,id;
namespace GP
{ 
   
	struct node
	{ 
   
		int ver,next;
	}e[N];
	int tot,head[N];
	void init()
	{ 
   
		for(re i=0;i<=n+1;i++)  head[i]=0;
		tot=1;
	}
	void add(int x,int y)
	{ 
   
		e[++tot].ver=y;
		e[tot].next=head[x];
		head[x]=tot;
	}
	void addedge(int x,int y)
	{ 
   
		add(x,y);add(y,x);
	}
	ll dfs(int x,int pre)
	{ 
   
		ll a[N];
		ll ans=1ll*N,top=0;
		for(re i=head[x];i;i=e[i].next)
		{ 
   
			int y=e[i].ver;
			if(y==pre)  continue;
			a[++top]=dfs(y,x);
		}
		sort(a+1,a+top+1);
		for(re i=1;i<=top;i++)  ans=ans*2333+a[i];
		return ans*2333+N+1;
	}
}
void solve()
{ 
   
	id++;
	cin>>n;
	GP::init();
	for(re i=1;i<=n;i++)
	{ 
   
		int x;
		scanf("%d",&x);
		if(x!=0)  GP::addedge(x,i);
	}
	for(re i=1;i<=n;i++)  ans[id][i]=GP::dfs(i,0);
	sort(ans[id]+1,ans[id]+n+1); 
	for(re j=1,k=0;j<=id;j++)
    { 
   
        while(k<=n)  if(ans[id][++k]!=ans[j][k])  break;
        if(k>n)
		{ 
   
			printf("%d\n",j);
			break;
		}	
    }
}
signed main()
{ 
   
// freopen("P1505_1.txt", "r", stdin);
// freopen("Aout.txt", "w", stdout);
    int T=1;
    cin>>T;
    for(int index=1;index<=T;index++)
    { 
   
// printf("Case #%lld: ",index);
        solve();
// puts("");
    }
    return 0;
}
/* 10 5 hbtngdflmj 1 10 1 2 9 0 3 8 1 4 7 0 5 6 1 */