Description：

Solution：

Code：

#include<algorithm>

#include<iostream>

#include<cstdlib>

#include<cstdio>

#include<cmath>

#include<cctype>

#include<cstring>

using namespace std;

inline int read()

{

	register int res = 0,f = 1;

	register char c = getchar();

	while(!isdigit(c))

	{

		if(c == '-')f = -1;

		c = getchar();

	}

	while(isdigit(c))

	{

		res = (res << 1) + (res << 3) + c - '0';

		c = getchar();

	}

	return res * f;

}

#define MAXN 110

int n,m;

int f[MAXN],g[MAXN];

int get(int x){return f[x] == -1 ? 0 : g[x] + get(f[x]);}

int find(int x)

{

	if(f[x] == -1)return x;

	int p = get(f[x]);

	g[x] = g[x] + p;f[x] = find(f[x]);

	return f[x];

}

bool tag;

void merge(int a,int b,int c)

{

	int p = find(a),q = find(b);

	if(p != q)

	{

		f[q] = p;

		g[q] = c + get(a) - get(b);

	}

	else

	{

		if(get(b) - get(a) != c)

		{

			tag = false;

		}

	}

	return;

}

void work()

{

	scanf("%d%d",&n,&m);

	memset(f,-1,sizeof(f));

	memset(g,0,sizeof(g));

	int a,b,c;

	tag = true;

	for(register int i = 1;i <= m;++i)

	{

		a = read();b = read();c = read();

		merge(a - 1,b,c);

	} 

	if(tag)puts("true");

	else puts("false");

	return;

}

int main()

{

	int testcases;

	scanf("%d",&testcases);

	while(testcases--)work();

	return 0;

}