HDU 6125 Free from square dp （看题解）

HDU 6125

把前八个素数状压， 后面的素数组内最多取一个， 所以分组背包， 没想到呀。。

#include<bits/stdc++.h>
#define LL long long
#define LD long double
#define ull unsigned long long
#define fi first
#define se second
#define mk make_pair
#define PLL pair<LL, LL>
#define PLI pair<LL, int>
#define PII pair<int, int>
#define SZ(x) ((int)x.size())
#define ALL(x) (x).begin(), (x).end()
#define fio ios::sync_with_stdio(false); cin.tie(0);

using namespace std;

const int N = 500 + 7;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e9 + 7;
const double eps = 1e-8;
const double PI = acos(-1);

template<class T, class S> inline void add(T &a, S b) {a += b; if(a >= mod) a -= mod;}
template<class T, class S> inline void sub(T &a, S b) {a -= b; if(a < 0) a += mod;}
template<class T, class S> inline bool chkmax(T &a, S b) {return a < b ? a = b, true : false;}
template<class T, class S> inline bool chkmin(T &a, S b) {return a > b ? a = b, true : false;}

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int n, k, state[N];
int who[N];

vector<int> sml, big[N];

int prime[] = {2, 3, 5, 7, 11, 13, 17, 19};

void init() {
    for(int i = 2; i <= 500; i++) {
        bool flag = true;
        int x = i;
        for(int j = 2; j * j <= x; j++) {
            if(x % (j * j) == 0) {
                flag = false;
                break;
            }
        }
        if(!flag) {
            state[i] = -1;
            continue;
        }
        for(int j = 0; j < 8; j++) {
            if(x % prime[j] == 0) {
                state[i] |= 1 << j;
                x /= prime[j];
            }
        }
        if(x > 1) who[i] = x;
    }
}

int dp[2][501][1 << 8];
int (*f)[1 << 8] = dp[0];
int (*g)[1 << 8] = dp[1];

int main() {
    init();
    int T; scanf("%d", &T);
    while(T--) {
        scanf("%d%d", &n, &k);
        sml.clear();
        for(int i = 1; i <= n; i++) {
            big[i].clear();
        }
        for(int i = 1; i <= n; i++) {
            if(state[i] == -1) {
                continue;
            }
            else if(who[i] == 0) {
                sml.push_back(i);
            }
            else {
                big[who[i]].push_back(i);
            }
        }

        for(int l = 0; l <= k; l++) {
            for(int mask = 0; mask < (1 << 8); mask++) {
                f[l][mask] = 0;
            }
        }

        f[0][0] = 1;

        for(auto v : sml) {
            swap(f, g);
            for(int l = 0; l <= k; l++) {
                for(int mask = 0; mask < (1 << 8); mask++) {
                    f[l][mask] = 0;
                }
            }
            for(int l = 0; l <= k; l++) {
                for(int mask = 0; mask < (1 << 8); mask++) {
                    add(f[l][mask], g[l][mask]);
                    if(mask & state[v]) continue;
                    add(f[l + 1][mask | state[v]], g[l][mask]);
                }
            }
        }

        for(int i = 1; i <= n; i++) {
            if(!SZ(big[i])) continue;
            swap(f, g);
            for(int l = 0; l <= k; l++) {
                for(int mask = 0; mask < (1 << 8); mask++) {
                    f[l][mask] = 0;
                }
            }
            for(int l = 0; l <= k; l++) {
                for(int mask = 0; mask < (1 << 8); mask++) {
                    if(!g[l][mask]) continue;
                    add(f[l][mask], g[l][mask]);
                    for(auto v : big[i]) {
                        if(mask & state[v]) continue;
                        add(f[l + 1][mask | state[v]], g[l][mask]);
                    }
                }
            }
        }
        
        int ans = 0;
        for(int l = 1; l <= k; l++) {
            for(int mask = 0; mask < (1 << 8); mask++) {
                add(ans, f[l][mask]);
            }
        }
        printf("%d
", ans);
    }
    return 0;
}

/*
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