HDU 6185(打表代码

/** @xigua */
#include <cstdio>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <vector>
#include <stack>
#include <cstring>
#include <queue>
#include <set>
#include <string>
#include <map>
#include <climits>
#define PI acos(-1)
using namespace std;
typedef long long LL;
typedef double db;
const int maxn = 1e5 + 5;
const int mod = 1e9 + 7;
const int INF = 1e8 + 5;
const LL inf = 1e15 + 5;
const db eps = 1e-6;
int mp[15][15];
int vis[15][15];
int n;
LL sum=0;
int cnt=0;

bool safe(int x, int y) {
    if (x>=0&&x<4&&y>=0&&y<n&&!vis[x][y])  return 1;
    return 0;
}
bool check() {
    for (int i=0; i<4; i++) {
        for (int j=0; j<n; j++) {
            if (!vis[i][j])  {
                return 0;
            }
        }
    }
    return 1;
}
int findx() {
    for (int i=0; i<4; i++) {
        for (int j=0; j<n; j++) {
            if (!vis[i][j])  {
                return i;
            }
        }
    }
    return -1;
}
int findy() {
    for (int i=0; i<4; i++) {
        for (int j=0; j<n; j++) {
            if (!vis[i][j])  {
                return j;
            }
        }
    }
    return -1;
}
void dfs(int x, int y) {
    for (int k=0; k<2; k++) {
        if (k==0) { //1*2
            if(safe(x,y)&&safe(x+1,y)) {
                vis[x][y]=2, vis[x+1][y]=2;
                if (check())  {
                    sum++;
                    vis[x][y]=0, vis[x+1][y]=0;
                }
                else {
                    int xx=findx(), yy=findy();
                    if(xx!=-1&&yy!=-1) {
                        vis[x][y]=2, vis[x+1][y]=2;
                        dfs(xx,yy);
                        vis[x][y]=0, vis[x+1][y]=0;
                    }
                }

            }
        }
        if (k==1) {  //2*1
            if (safe(x,y)&&safe(x,y+1)) {
                vis[x][y]=1, vis[x][y+1]=1;
                    if (check())  {
                        sum++;
                        vis[x][y]=0, vis[x][y+1]=0;
                    }
                    else {
                            vis[x][y]=1, vis[x][y+1]=1;
                        int xx=findx(), yy=findy();
                        if(xx!=-1&&yy!=-1) {
                            dfs(xx,yy);
                            vis[x][y]=0, vis[x][y+1]=0;
                        }
                    }
            }
        }
    }
}
void solve() {
    scanf("%d", &n);
    sum=0;  cnt=0;
    memset(vis, 0, sizeof(vis));
    dfs(0, 0);
    cout<<"sum:"<<sum<<endl;
}
int main() {
    int t = 1, cas = 1;
    //freopen("in.txt", "r", stdin);
   // freopen("out.txt", "w", stdout);
    //scanf("%d", &t);
    while(t--) {
       // printf("Case %d: ", cas++);
        solve();
    }
    return 0;
}