小国王(状压dp经典题)

#include <bits/stdc++.h>
using namespace std;
int n, m;
const int N = 15;
long long dp[N][1100][1 << 13]; //目前的行 选了多少个 目前状态
vector<int>v;//每行压缩航的合法状态
int check(int x)
{
  int res = 0;
  for (int i = 0; i <= 31; i++)
  {
    if (x >> i & 1) res++;
  }
  return res;
}
int main()
{
  cin >> n >> m;
  int ans = 0;
  for (int i = 0; i < (1 << n); i++)
  {
    if ((i & (i << 1)) == 0)
    {
      v.push_back(i);
    }
  }
  int len = v.size();
  //for(int i=0;i<len;i++)
  //dp[1][check(v[i])][i]=1;
  dp[0][0][0] = 1;
  for (int i = 1; i <= n + 1; i++)
  {
    for (int l = 0; l <= m; l++)
      for (int j = 0; j < len; j++)
      {
        for (int k = 0; k < len; k++)
        {
          if (v[j]&v[k]) continue;
          int t = v[j] | v[k];
          if (t & (t << 1)) continue;
          if (l - check(v[j]) < 0) continue;
          dp[i][l][j] += dp[i - 1][l - check(v[j])][k];
        }
      }
  }
  cout << dp[n + 1][m][0] << endl;
}