[DP] Codeforces 840C .On the Bench

%%%Vectorxj

#include <cstdio>#include <iostream>#include <algorithm>#include <map>#include <vector>using namespace std;const int N=610,P=1e9+7;int n,x,f[2][N];map<int,int> mp;vector<int> a;int fac[N],inv[N];inline int C(int x,int y){    return 1LL*fac[x]*inv[y]%P*inv[x-y]%P;}inline void add(int &x,int y){    if((x+=y)>=P) x-=P;}int main(){    freopen("1.in","r",stdin);    freopen("1.out","w",stdout);    scanf("%d",&n);    fac[0]=inv[0]=inv[1]=1;    for(int i=1;i<=600;i++) fac[i]=1LL*i*fac[i-1]%P;    for(int i=2;i<=600;i++) inv[i]=1LL*(P-P/i)*inv[P%i]%P;    for(int i=1;i<=600;i++) inv[i]=1LL*inv[i]*inv[i-1]%P;    for(int i=1;i<=n;i++){        scanf("%d",&x);        for(int j=2;j*j<=x;j++)            while(x%(j*j)==0) x/=j*j;        mp[x]++;    }    for(auto i : mp) a.push_back(i.second);    int s=0,tot=a[0]; f[s][a[0]-1]=1;    for(int g=1;g<a.size();g++,s^=1){        int nxt=a[g];        for(int i=0;i<=n;i++) f[s^1][i]=0;        for(int i=0;i<tot;i++)            for(int j=1;j<=nxt;j++)                for(int k=0;k<=j && k<=i;k++)                    if(tot-i+1>=j-k)                        add(f[s^1][i-k+nxt-j],1LL*f[s][i]*C(i,k)%P*C(tot-i+1,j-k)%P*C(nxt-1,j-1)%P);        tot+=nxt;    }    for(int i : a) f[s][0]=1LL*f[s][0]*fac[i]%P;    printf("%d\n",f[s][0]);    return 0;}