[cogs 2190]花样游戏

来源：互联网发布：兵人淘宝店编辑：程序博客网时间：2024/04/20 09:34
FWT
#define MAXN 200010#include <cstdio> using namespace std;typedef long long ll;const int md = 1e9 + 7, inv2 = 500000004;int power_mod(int a, int b = md - 2) {    int ret = 1;    while(b > 0) {        if(b & 1) ret = (ll)ret * a % md;        b >>= 1;        a = (ll)a * a % md;    }return ret;}void fwt(int* A, int n) {    for(int k = 1 ; k <= n ; k <<= 1) {        int t = k>>1;        for(int i = 0 ; i <= n ; i += k) {            for(int j = 0 ; j < t ; j ++) {                int x = A[i+j], y = A[i+j+t];                A[i+j] = (x + y) % md;                A[i+j+t] = (x - y) % md;            }        }    }}void ifwt(int* A, int n) {    for(int k = 1 ; k <= n ; k <<= 1) {        int t = k>>1;        for(int i = 0 ; i <= n ; i += k) {            for(int j = 0 ; j < t ; j ++) {                int x = A[i+j], y = A[i+j+t];                A[i+j] = (ll)(x + y) * inv2 % md;                A[i+j+t] = (ll)(x - y) * inv2 % md;            }        }    }}int f[MAXN], p[MAXN], primes, n, m;bool vis[MAXN];int main() {    freopen("srmnim.in", "r", stdin);    freopen("srmnim.out", "w", stdout);    n = 60000;    for(int i = 2 ; i <= n ; ++ i) {        if(!vis[i]) p[++ primes] = i;        for(int j = 1 ; j <= primes ; ++ j) {            if(1ll * i * p[j] > n)break;            vis[i * p[j]] = true;            if(i % p[j] == 0)break;        }    }    while(~ scanf("%d%d", &n, &m)) {        int N = 1;        for( ; N <= m ; N <<= 1);        for(int i = 0 ; i < N ; ++ i)f[i] = 0;        for(int i = 1 ; p[i] <= m ; ++ i)            f[p[i]] = 1;        fwt(f, N);        for(int i = 0 ; i < N ; ++ i)            f[i] = power_mod(f[i], n);        ifwt(f, N);        printf("%d\n", (f[0]+md)%md);    }    return 0;}
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