BZOJ 1016: [JSOI2008]最小生成树计数
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/* BZOJ 1016: [JSOI2008]最小生成树计数 对原图做一遍Kruskal最小生成树,统计不同边使用的次数 每次暴力统计一下 答案乘一乘就好了 */ #include <cstdio> #include <iostream> #include <algorithm> #define rg register #define Mod 31011 #define Max 1009 inline void read (int &n) { rg char c = getchar (); for (n = 0; !isdigit (c); c = getchar ()); for (; isdigit (c); n = n * 10 + c - ‘0‘, c = getchar ()); } struct E { int u, v, d; bool operator < (const E &rhs) const { return d < rhs.d; } } e[Max]; int f[Max / 10 + 3], C, T, p; struct D { int v, s, l, r; } g[Max]; int Find (int x) { return f[x] == x ? x : Find (f[x]); } void Dfs (int n, int t, int i) { if (n == g[i].r + 1) { if (t == g[i].s) ++ p; return ; } Dfs (n + 1, t, i); int x = Find (e[n].u), y = Find (e[n].v); if (x != y) f[x] = y, Dfs (n + 1, t + 1, i), f[x] = x; } int main (int argc, char *argv[]) { int N, M, x, y, r, s = 1; read (N), read (M); rg int i, j; for (i = 1; i <= M; ++ i) read (e[i].u), read (e[i].v), read (e[i].d); std :: sort (e + 1, e + 1 + M); for (i = 1; i <= N; f[i] = i, ++ i); for (i = 1; i <= M; ++ i) { if (e[i].d != g[C].v) g[C].r = i - 1, g[++ C].l = i, g[C].v = e[i].d; x = Find (e[i].u), y = Find (e[i].v); if (x != y) f[x] = f[y], ++ T, ++ g[C].s; if (T == N - 1) { r = i; break; } } if (T != N - 1) return printf ("0"), 0; for (i = r + 1; i <= M; ++ i) if (e[i].d == g[C].v) r = i; for (g[C].r = r, i = 1; i <= N; f[i] = i, ++ i); for (i = 1; i <= C; ++ i) { if (g[i].s == 0) continue; p = 0, Dfs (g[i].l, 0, i), s = s * p % Mod; for (j = g[i].l; j <= g[i].r; ++ j) { x = Find (e[j].u), y = Find (e[j].v); if (x != y) f[x] = y; } } printf ("%d", s); return 0; }
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