iiitv/ChefLib

#include < bits/stdc++.h >

//____By:sirjan13____

#define ll long long int
#define mod 1000000007
#define show(a) for(i=0;i<a.size();i++) cout<<a[i]<<" ";
#define fi first
#define se second
#define vi vector<int>
#define vs vector<string>
#define vll vector<long long int>
#define pb push_back
#define pi pair<int,int>
#define si set< int >
#define sll set< ll >
#define maxheap priority_queue< int >
#define minheap priority_queue< int,vector< int >,greater< int > >
#define mp make_pair
#define fast_io() cin.sync_with_stdio(false);cout.sync_with_stdio(false);
#define long_zero 0ll
#define long_one 1ll

inline int sbt(int x){return __builtin_popcount(x);}

using namespace std;

struct cell {
    int nind;
    int x;
};

bool v[100002];
int arr[100002];
bool fff=false;

vector< cell > a[100002];

void f( int p,int current ){
    v[ current ]=true;
    for(int i=0;i<a[current].size();i++){
        if ( !v[a[current][i].nind] ) {
            arr[a[current][i].nind]=a[current][i].x+arr[current];
            f(current,a[current][i].nind);
        }
        else if ( p!=a[current][i].nind ){
            if( ( arr[ current ] + a[ current ][ i ].x - arr[a[current][i].nind]) & 1 ) {
                fff = true;
                return;
            }
        }
    }
}
void freespace(int n){
    for(int i = 1 ;i <= n; i++) a[i].clear();
}
int main() {
    fast_io()
    int t;
    cin >> t;

    while ( t-- ){
        memset (v, false, sizeof(v));
        int n,m,r,c,va;
        cin >> n >>m;
        fff=false;
        memset(arr,0,sizeof(arr));
        for(int i=0;i<m;i++){
            cin >> r >> c >> va;
            cell nwc;
            nwc.nind=c;
            nwc.x=va;
            a[r].pb(nwc);
            cell nw2c;
            nw2c.x=va;
            nw2c.nind=r;
            a[c].pb(nw2c);
        }
        for(int i=1;i<=n;i++){
            if(!v[i]){
                f(0,i);
                if(fff){
                    break;
                }
            }
        }
        freespace(n);
        if(fff)
            cout << "no";
        else
            cout << "yes";
        cout<<endl;
    }
    return 0;
}