[搜索]Connect3

#include <iostream>
#include<cstdio>
#include<map>
using namespace std;

int x,a,b;
int ans=0;
int board[10][10];
int black,white;
map<pair<int,int>,int> mp;

int get_loc(int x,int y) {return 4*(x-1)+y;}

bool check(int p){
  for(int i=1;i<=4;i++){
    for(int j=1;j<=4;j++){
        if(i<=2&&board[i][j]==p&&board[i+1][j]==p&&board[i+2][j]==p) return 1;
        if(j<=2&&board[i][j]==p&&board[i][j+1]==p&&board[i][j+2]==p) return 1;
        if(i<=2&&j<=2&&board[i][j]==p&&board[i+1][j+1]==p&&board[i+2][j+2]==p) return 1;
        if(i<=2&&j>=3&&board[i][j]==p&&board[i+1][j-1]==p&&board[i+2][j-2]==p) return 1;
    }
  }
  return 0;
}

void dfs(int x,int y,int turn){
  board[x][y]=turn;
  int cop1=black,cop2=white;
  black=black|((turn==2)<<(get_loc(x,y)-1));
  white=white|((turn==3)<<(get_loc(x,y)-1));
  if(check(2)){
    board[x][y]=0,black=cop1,white=cop2;
    return;
  }
  if(check(3)){
    if(x==a&&y==b) ans++;
    board[x][y]=0,black=cop1,white=cop2;
    return;
  }
  if(mp[make_pair(black,white)]){//判重必需在以上两个check之后
    board[x][y]=0,black=cop1,white=cop2;
    return;
  }
  mp[make_pair(black,white)]=1;
  for(int j=1;j<=4;j++){
    for(int i=1;i<=4;i++){
        if(!board[i][j]&&(i==1||(i>=2&&board[i-1][j]))){
            dfs(i,j,turn^1);
        }
    }
  }
  board[x][y]=0,black=cop1,white=cop2;
}

int main()
{
    scanf("%d%d%d",&x,&a,&b);
    dfs(1,x,2);
    printf("%d\n",ans);
    return 0;
}