洛谷AT3882

#include<iostream>
using namespace std;
const int maxn = 1e7+5;
int pre[maxn],dis[maxn];
//错误 
int find(int x){
    while(x!=pre[x]){
        int r = pre[x];
        pre[x] = pre[r];
        dis[x] += dis[r];
        x = r;
    }
    return x;
}
//int find(int x){
//    if(x==pre[x]){
//        return x;
//    }
//    int r = find(pre[x]);
//    dis[x] += dis[pre[x]];
//    return pre[x] = r;
//} 
bool merge(int x,int y,int d){
    int px = find(x);
    int py = find(y);
    if(px==py){
        return d==(dis[y]-dis[x]);
    }
    pre[py] = px ;
    dis[py] = dis[x]+d-dis[y];
    return true;
}
void init(){
    for(int i=0;i<maxn;i++){
        pre[i] = i;
    }
}
int main()
{
    init(); 
    int n,m,ans=1;
    cin>>n>>m;
    for(int i=0;i<m;i++){
        int x,y,d;
        cin>>x>>y>>d;
        if(ans){
            ans = merge(x,y,d);
        }
    }

    if(ans){
        cout<<"Yes"<<endl;
    }else{
        cout<<"No"<<endl; 
    }
    return 0;
}