CF1850H

 

带权并查集板题

 

维护到根的距离

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#include <iostream> #include <algorithm> #include <cstring> #include <vector> #include <queue> using namespace std; const int N =2e5+10; #define int long long int n,fa[N],dis[N]; int find(int x){     if(x==fa[x]) return x;           int t =find(fa[x]) ;     dis[x]+=dis[fa[x]] ;     fa[x]=t ;     return fa[x] ; }   void join(int x,int y,int v){     int fx = find(x), fy= find(y) ;     fa[fx] =fy ;     dis[fx] = v+dis[y]-dis[x] ; } void sov(){     int q ,flg=1;     cin>>n>>q;     for(int i=1;i<=n;i++) fa[i]=i,dis[i]=0 ;     while(q--){         int x,y,d ;         cin>>x>>y>>d;         int fx =find(x), fy =find(y) ;         if(fx==fy){             if(d!=dis[x]-dis[y]) flg =0 ;         }         else{             join(x,y,d);         }     }           if(flg) cout<<"YES\n";else cout<<"NO\n" ; }   signed main(){     int T; cin>>T; while(T--) sov() ; }