【BZOJ 1875】【SDOI 2009】HH去散步

標籤：

水啊水，最後ans別忘了%哦！

#include<cstdio>#include<cstring>#include<algorithm>using namespace std;const int mo = 45989;int cnt = 1, point[23], n, m, t, S, T;struct node {int u, v, nxt;} E[1003];struct Mt {int v[123][123];Mt() {memset(v, 0, sizeof(v));}friend Mt operator * (Mt a, Mt b) {Mt ans;for(int i = 1; i <= cnt; ++i)for(int j = 1; j <= cnt; ++j)for(int k = 1; k <= cnt; ++k)ans.v[i][j]=(ans.v[i][j] + a.v[i][k] * b.v[k][j]) % mo;return ans;}friend Mt operator ^ (Mt a, int b) {Mt ans;for(int i = 1; i <= cnt; ++i)ans.v[i][i] = 1;for(int i = b; i; i >>= 1, a = a * a)if (i & 1) ans = ans * a;return ans;}}A, B;inline void ins(int x, int y) {E[++cnt].u = x; E[cnt].v = y; E[cnt].nxt = point[x]; point[x] = cnt;}int main() {scanf("%d%d%d%d%d", &n, &m, &t, &S, &T);int u, v;for(int i = 1; i <= m; ++i) {scanf("%d%d", &u, &v);ins(u, v);ins(v, u);}for(int tmp = point[S]; tmp; tmp = E[tmp].nxt)++A.v[1][tmp];for(int i = 2; i <= cnt; ++i)for(int j = 2; j <= cnt; ++j)if (E[i].v == E[j].u && i != (j ^ 1))++B.v[i][j];A = A * (B ^ (t - 1));int ans = 0;for(int tmp = point[T]; tmp; tmp = E[tmp].nxt)ans += A.v[1][tmp ^ 1];printf("%d\n", ans % mo);return 0;}

hhh

【BZOJ 1875】【SDOI 2009】HH去散步