带权并查集

Posted 2021-05-27 LH2000

[HNOI2005]狡猾的商人 - 题目 - 黑暗爆炸OJ (darkbzoj.tk)

注意维护的是边而不是点

s需要-1

 

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int mod=998244353;
const int N=200005;
int prime[1100000],primesize;
bool isprime[11000000];
ll f[N],invf[N];
ll inv[N];
void getlist(int listsize){
    memset(isprime,1,sizeof(isprime));
    isprime[1]=false;
    for(int i=2;i<=listsize;i++){
        if(isprime[i])prime[++primesize]=i;
         for(int j=1;j<=primesize&&i*prime[j]<=listsize;j++) {
            isprime[i*prime[j]]=false;
            if(i%prime[j]==0) break;
        }
    }
}
void extend_gcd(ll a, ll b, ll& d, ll& x, ll& y)
{
    if(!b){ d = a; x = 1; y = 0; }
    else { extend_gcd(b, a%b,d, y, x); y -= x*(a/b);}
}
void ni(int n)
{
    inv[0] = inv[1] = 1;
    for(int i = 2; i <= n; i++)
    {
        inv[i] = (mod - (mod/i))*inv[mod%i]%mod;
    }
}
ll fpow(ll a,ll k){
    ll res=1;
    while(k){
        if(k&1) res=(res*a)%mod;
        k>>=1;
        a=a*a%mod;
        //cout<<1<<endl;
    }
    return res;
}
ll mm(ll a,ll b){
    ll ret=0;
    for(a%=mod;b;b>>=1){
        if(b&1){ret+=a;if(ret>=mod)ret-=mod;}
        a<<=1;if(a>=mod)a-=mod;
    }
    return ret;
}
void init(int n){
    f[0]=1;
    for(int i=1;i<=n;++i){
        f[i]=f[i-1]*i%mod;
    }
    invf[n]=fpow(f[n],mod-2);
    for(int i=n-1;i>=0;--i){
        invf[i]=invf[i+1]*(i+1)%mod;
    }
}
ll C(int n,int k){
    if(k<0 || k>n) return 0;
    return f[n]*invf[k]%mod*invf[n-k]%mod;
}
ll d[1005];
ll fa[1005];
ll ff(ll x){
    if(x==fa[x])return x;
    ll xx=ff(fa[x]);
    d[x]+=d[fa[x]];
    return fa[x]=xx;
}
void solve(){
    ll n,m;
    cin>>n>>m;
    memset(d,0,sizeof(d));
    for(int i=0;i<=n;i++){
        fa[i]=i;
    } 
    int flag=1;
    for(int i=1;i<=m;i++){
        ll s,t,v;
        cin>>s>>t>>v;
        s--;
        ll xx=ff(s);
        ll yy=ff(t);
        if(xx!=yy){
            fa[yy]=xx;
            d[yy]=d[s]-d[t]+v;
        }
        else if(d[t]-d[s]!=v){
            flag=0;
            break;
        }
    }
    if(flag){
        cout<<"true"<<endl;
    }
    else{
        cout<<"false"<<endl;
    }
}
int main(){
    ios::sync_with_stdio(false);cin.tie(0);
//    freopen("1.in","r",stdin);
//    getlist(1e7);
    int t=1;
    cin>>t;
    while(t--){
        solve();
    }
}