Questions surface: https://www.luogu.org/problemnew/show/P1896
Classic shaped pressure dp, dp equation: f [i] [j] [k] + = f [i-1] [j-num [k]] [l];
There bit operation it is also important to determine
Code:
#include<iostream>
#include<cstdio> #include<cstring> #include<cmath> #include<cstdlib> #include<algorithm> #include<bitset> #include<ctime> #include<stack> using namespace std; const int N=10005,M=15; long long n,k1,num[N],s[N],f[M][M][N],tot,ans; long long lowbit(long long x){ return x&(-x); } int main(){ scanf("%lld%lld",&n,&k1); for(int i=0;i<(1<<n);i++){ if(!(i&(i<<1))){ int sum=0,t=i; ++tot; while(t){ t-=lowbit(t); ++sum; } num[tot]=sum; s[tot]=i; } } for(int i=1;i<=tot;i++){ if(num[i]>k1) continue; f[1][num[i]][i]=1; } for(int i=2;i<=n;i++){ for(int j=0;j<=k1;j++){ for(int k=1;k<=tot;k++){ if(num[k]>j) continue; for(int l=1;l<=tot;l++){ if(num[l]>j-num[k]) continue; if(s[k]&s[l]) continue; if(s[k]&(s[l]<<1)) continue; if(s[l]&(s[k]<<1)) continue; f[i][j][k]+=f[i-1][j-num[k]][l]; } } } } for(int j=1;j<=tot;j++){ ans+=f[n][k1][j]; } printf("%lld\n",ans); return 0; }