题解，求关注

#include <cstdio>
#include <algorithm>

#define fr first
#define sc second

const int MOD = 31011, MAXN = 100, MAXM = 1000;
int n, m, fa[MAXN + 5], col[MAXN + 5], K[MAXN + 5][MAXN + 5];
bool used[MAXM + 5];
std::pair<int, std::pair<int, int> > eset[MAXM + 5];

inline void init ( const int n ) { for ( int i = 1; i <= n; ++ i ) fa[i] = i; }

inline int find ( const int x ) { return x ^ fa[x] ? fa[x] = find ( fa[x] ) : x; }

inline bool unite ( const int a, const int b ) {
	int u = find ( a ), v = find ( b );
	return u ^ v ? fa[u] = v, true : false;
}

inline void add ( const int u, const int v ) {
	++ K[u][u], ++ K[v][v], -- K[u][v], -- K[v][u];
	if ( K[u][v] < 0 ) K[u][v] += MOD;
	if ( K[v][u] < 0 ) K[v][u] += MOD;
}

inline int det ( const int n ) {
	int ret = 1, swp = 1;
	for ( int i = 1; i < n; ++ i ) {
		for ( int j = i + 1; j < n; ++ j ) {
			for ( ; K[j][i]; std::swap ( K[i], K[j] ), swp *= -1 ) {
				int d = K[i][i] / K[j][i];
				for ( int k = i; k < n; ++ k ) K[i][k] = ( K[i][k] - d * K[j][k] + MOD ) % MOD;
			}
		}
		if ( ! ( ret = ret * K[i][i] % MOD ) ) return 0;
	}
	return ( ret * swp + MOD ) % MOD;
}

int main () {
	scanf ( "%d %d", &n, &m );
	for ( int i = 1, u, v, w; i <= m; ++ i ) {
		scanf ( "%d %d %d", &u, &v, &w );
		eset[i] = { w, { u, v } };
	}
	sort ( eset + 1, eset + m + 1 ), init ( n );
	int cnt = 0;
	for ( int i = 1; i <= m && cnt < n - 1; ++ i ) {
		if ( unite ( eset[i].sc.fr, eset[i].sc.sc ) ) {
			++ cnt, used[i] = true;
		}
	}
	if ( cnt < n - 1 ) return puts ( "0" ), 0;
	int ans = 1;
	for ( int i = 1, j; i <= m; i = j + 1 ) {
		init ( n );
		for ( j = 1; j <= m; ++ j ) {
			if ( used[j] && eset[i].fr ^ eset[j].fr ) {
				unite ( eset[j].sc.fr, eset[j].sc.sc );
			}
		}
		int blk = 0;
		for ( j = 1; j <= n; ++ j ) if ( j == fa[j] ) col[j] = ++ blk;
		for ( j = 1; j <= n; ++ j ) col[j] = col[find ( j )];
		for ( j = 1; j <= blk; ++ j ) for ( int k = 1; k <= blk; ++ k ) K[j][k] = 0;
		for ( j = i; j <= m; ++ j ) {
			add ( col[eset[j].sc.fr], col[eset[j].sc.sc] );
			if ( j == m || eset[j].fr ^ eset[j + 1].fr ) break;
		}
		ans = ans * det ( blk ) % MOD;
	}
	printf ( "%d\n", ans );
	return 0;
}