洛谷 P1784 数独

题目传送门

解题思路:

跟八皇后很相似,区别在于本题不用记录斜线,但是要记录每个宫格,在每个位置上都要填数.

AC代码：

#include<cstdio>
#include<iostream>
#include<cstdlib>

using namespace std;

int a[10][10];
bool h[10][10],l[10][10],g[10][10]; 

inline void print() {
    for(int i = 1;i <= 9; i++) {
        for(int j = 1;j <= 9; j++)
            printf("%d ",a[i][j]);
        printf("
");
    }
    exit(0);
}

inline void dfs(int x,int y) {
    if(a[x][y] != 0) {
        if(x == 9 && y == 9)
            print();
        else
            if(y == 9) 
                dfs(x + 1,1);
            else 
                dfs(x,y + 1);
    }
    if(a[x][y] == 0) {
        for(int i = 1;i <= 9; i++) {
            if(!h[i][x] && !l[i][y] && !g[i][(x-1)/3*3+(y-1)/3+1]) {
                a[x][y] = i;
                h[i][x] = 1;
                l[i][y] = 1;
                g[i][(x-1)/3*3+(y-1)/3+1] = 1;
                if(x == 9 && y == 9)
                    print();
                if(y == 9)
                    dfs(x + 1,1);
                else
                    dfs(x,y + 1);
                a[x][y] = 0;
                h[i][x] = 0;
                l[i][y] = 0;
                g[i][(x-1)/3*3+(y-1)/3+1] = 0;
            }
        }
    }
}

int main()
{
    for(int i = 1;i <= 9; i++)
        for(int j = 1;j <= 9; j++){ 
            scanf("%d",&a[i][j]);
            h[a[i][j]][i] = l[a[i][j]][j] = g[a[i][j]][(i-1)/3*3+(j-1)/3+1] = 1;
        } 
    dfs(1,1);
    return 0;
}