Luo Gu P1784 Sudoku

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Problem-solving ideas:

With eight queens is very similar, except that this question without recording a slash, but to record each grids, should fill the number in each position.

AC Code:

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<cstdlib>
 4 
 5 using namespace std;
 6 
 7 int a[10][10];
 8 bool h[10][10],l[10][10],g[10][10]; 
 9 
10 inline void print() {
11     for(int i = 1;i <= 9; i++) {
12         for(int j = 1;j <= 9; j++)
13             printf("%d ",a[i][j]);
14         printf("\n");
15     }
16     exit(0);
17 }
18 
19 inline void dfs(int x,int y) {
20     if(a[x][y] != 0) {
21         if(x == 9 && y == 9)
22             print();
23         else
24             if(y == 9) 
25                 dfs(x + 1,1);
26             else 
27                 dfs(x,y + 1);
28     }
29     if(a[x][y] == 0) {
30         for(int i = 1;i <= 9; i++) {
31             if(!h[i][x] && !l[i][y] && !g[i][(x-1)/3*3+(y-1)/3+1]) {
32                 a[x][y] = i;
33                 h[i][x] = 1;
34                 l[i][y] = 1;
35                 g[i][(x-1)/3*3+(y-1)/3+1] = 1;
36                 if(x == 9 && y == 9)
37                     print();
38                 if(y == 9)
39                     dfs(x + 1,1);
40                 else
41                     dfs(x,y + 1);
42                 a[x][y] = 0;
43                 h[i][x] = 0;
44                 l[i][y] = 0;
45                 g[i][(x-1)/3*3+(y-1)/3+1] = 0;
46             }
47         }
48     }
49 }
50 
51 int main()
52 {
53     for(int i = 1;i <= 9; i++)
54         for(int j = 1;j <= 9; j++){ 
55             scanf("%d",&a[i][j]);
56             h[a[i][j]][i] = l[a[i][j]][j] = g[a[i][j]][(i-1)/3*3+(j-1)/3+1] = 1;
57         } 
58     dfs(1,1);
59     return 0;
60 }