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#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<queue>
#include<cstring>
#include<algorithm>
#define rep(i,x,y) for(register int i=x;i<=y;++i)
#define repd(i,x,y) for(register int i=x;i>=y;--i)
#define ll long long
using namespace std;
const int N=1e5+7;
const int inf=0x3f3f3f3f;
int T,n,m,cnt;
int head[N],to[N],nxt[N],inq[N],w[N],dis[N],tot[N];
queue<int>q;
inline void (int a,int b,int c){
to[++cnt]=b;
w[cnt]=c;
nxt[cnt]=head[a];
head[a]=cnt;
}
int spfa(int u){
while(!q.empty())q.pop();
q.push(u);
inq[u]=1;dis[u]=0;
while(!q.empty()){
int k=q.front();q.pop();
inq[k]--;
for(int i=head[k];i;i=nxt[i])if(dis[to[i]]>dis[k]+w[i]){
dis[to[i]]=dis[k]+w[i];
tot[to[i]]++;
if(tot[to[i]]>=n)return 0;
if(!inq[to[i]]){
q.push(to[i]);
inq[to[i]]++;
}
}
}
return 1;
}
int main(){
scanf("%d",&T);
while(T--){
cnt=0;
memset(dis,0x3f,sizeof dis);
memset(inq,0,sizeof inq);
memset(head,0,sizeof head);
memset(tot,0,sizeof tot);
scanf("%d%d",&n,&m);
rep(i,1,m){
int a,b,c;
scanf("%d%d%d",&a,&b,&c);
adde(a-1,b,c);adde(b,a-1,-c);
}
int ans=0;
rep(i,0,n)if(!tot[i]&&!spfa(i)){ans=1;break;}
puts(ans?"false":"true");
}
return 0;
}
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