hdu 4408 Minimum Spanning Tree

#include <stdio.h>
#include <iostream>
#include <vector>

#define LL long long

using namespace std;

const int MAX = 105;
const int MAXE = 1005;

struct node
{
int set[MAX];
void init(int n)
{
for (int i = 0; i <= n; i++)
set[i] = i;
}
int find(int x)
{
if (set[x] != x)
set[x] = find(set[x]);
return set[x];
}
int Union(int x, int y)
{
int xx = find(x);
int yy = find(y);
if (xx == yy)
return -1;
set[xx] = yy;
return 1;
}
};

struct Node
{
int u, v, dis;
};

node a, b, c;
int n, m;
Node e[MAXE];
int visit[MAX];
vector<int> g[MAX];
LL p[MAX][MAX], MOD, deg[MAX][MAX];

bool cmp(Node a, Node b)
{
return a.dis < b.dis;
}

LL DET(LL a[][MAX], int n)
{
LL temp = 1, t;
for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
a[i][j] %= MOD;
for (int i = 1; i < n; i++)
{
for (int j = i + 1; j < n; j++)
while (a[j][i])
{
t = a[i][i] / a[j][i];
for (int k = i; k < n; k++)
{
a[i][k] -= a[j][k] * t;
a[i][k] %= MOD;
}
for (int k = i; k < n; k++)
{
t = a[i][k];
a[i][k] = a[j][k];
a[j][k] = t;
}
temp = -temp;
}
temp = temp * a[i][i] % MOD;
}
return (temp + MOD) % MOD;
}

LL cal_MST_cout()
{
sort(e + 1, e + m + 1, cmp);
int pre = e[1].dis;
LL ans = 1;
a.init(n);
b.init(n);
memset(visit, false, sizeof(visit));
memset(deg, false, sizeof(deg));
for (int i = 0; i <= n; i++)
g[i].clear();
for (int t = 1; t <= m + 1; t++)
{
if (e[t].dis != pre || t == m + 1)
{
for (int i = 1; i <= n; i++)
if (visit[i])
{
int k = b.find(i);
g[k].push_back(i);
visit[i] = 0;
}
for (int i = 1; i <= n; i++)
if (g[i].size())
{
memset(p, false, sizeof(p));
for (int j = 0; j < g[i].size(); j++)
for (int k = j + 1; k < g[i].size(); k++)
{
int x = g[i][j];
int y = g[i][k];
p[j][k] = p[k][j] = -deg[x][y];
p[j][j] += deg[x][y];
p[k][k] += deg[x][y];
}
ans = ans * DET(p, g[i].size()) % MOD;
for (int j = 0; j < g[i].size(); j++)
a.set[g[i][j]] = i;
}
memset(deg, false, sizeof(deg));
for (int i = 1; i <= n; i++)
{
b.set[i] = a.find(i);
g[i].clear();
}
if (t == m + 1)
break;
pre = e[t].dis;
}
int x = a.find(e[t].u);
int y = a.find(e[t].v);
if (x == y)
continue;
visit[x] = visit[y] = 1;
b.Union(x, y);
deg[x][y]++;
deg[y][x]++;
}
if (!m)
return false;
for (int i = 2; i <= n; i++)
if (b.find(i) != b.find(1))
return false;
return ans;
}

int main()
{
while (~scanf("%d%d%lld", &n, &m, &MOD) && (n | m | MOD))
{
for (int i = 1; i <= m; i++)
scanf("%d%d%d", &e[i].u, &e[i].v, &e[i].dis);
printf("%lld\n", cal_MST_cout());
}
}