acwing 166数独

acwing 166数独

问题

传送门

代码

#include <iostream>
#include <cstdio>
#include <queue>
#include <cstring>
using namespace std;
const int N = 9;
int ones[1<<N],map[1<<N];
int row[N],col[N],cell[N/3][N/3];
char str[100];
int lowbit(int x)
{
    return x&(-x);
}
void init()
{
    for(int i=0;i<N;i++)
    {
        row[i] = col[i] = (1<<N)-1;
    }
    for(int i=0;i<3;i++)
    {
        for(int j=0;j<3;j++)
        {
            cell[i][j] = (1<<N)-1;
        }
    }
}
int get(int x,int y)
{
    return row[x] & col[y] & cell[x/3][y/3];
}
bool dfs(int cnt)
{
    if(!cnt)
        return true;
    int minn = 10,x,y;
    for(int i=0;i<N;i++)
    {
        for(int j=0;j<N;j++)
        {
            if(str[i*9+j]=='.')
            {
                int cnt = ones[get(i,j)];
                if(minn>cnt)
                {
                    minn = cnt;
                    x = i;
                    y = j;
                }
            }
        }
    }
    for(int i=get(x,y);i;i-=lowbit(i))
    {
        int t = map[lowbit(i)];
        row[x] -= (1<<t);
        col[y] -= (1<<t);
        cell[x/3][y/3] -= (1<<t);
        str[x*9+y] = t+'1';
        if(dfs(cnt-1))
            return true;
        row[x] += (1<<t);
        col[y] += (1<<t);
        cell[x/3][y/3] += (1<<t);
        str[x*9+y] = '.';
    }
    return false;
}
int main() {
    for(int i=0;i<N;i++)
    {
        map[1<<i] = i;
    }
    for(int i=0;i<(1<<N);i++)
    {
        int sum = 0;
        for(int j=i;j;j-=lowbit(j))
        {
            sum++;
        }
        ones[i] = sum;
    }
    while(cin >> str,str[0]!='e')
    {
        init();
        int cnt=0;
        for(int i=0;i<N;i++)
        {
            for(int j=0;j<N;j++)
            {
                if(str[j+i*9]!='.')
                {
                    int cnt = str[j+i*9] - '1';
                    row[i] -= (1 << cnt);
                    col[j] -= (1 << cnt);
                    cell[i/3][j/3] -= (1<<cnt);
                }
                else
                {
                    cnt++;
                }
            }
        }
        dfs(cnt);
        cout << str << "
";
    }
    return 0;
}