Sudoku(dfs)
http://poj.org/problem?id=2676
填九宫格
思路：将每一行，每一列及每一个3*3块中出现的数字标记上，将可填的空的位置记录下来，枚举1-9，填入合适的数。
1 #include <stdio.h> 2 #include <string.h> 3 int row[10][10],col[10][10],arr[10][10];//row[x][i]表示i所在的行为x; 4 //col[y][i]表示i所在的列为y; 5 //arr[n][i]表示i所在的3*3方格; 6 int keep[82][2],map[10][10],num,t; //keep[][]记录可填数的位置; 7 void show() 8 { 9 for (int i = 0;i < 9;i ++) 10 { 11 for (int j = 0;j < 9;j ++) 12 { 13 printf("%d",map[i][j]); 14 } 15 puts(""); 16 } 17 } 18 int dfs(int x,int y) 19 { 20 if (t==num) 21 { 22 show(); 23 return 1; 24 } 25 for (int i = 1;i <= 9;i ++) 26 { 27 int k = x/3*3+y/3; 28 if (!row[x][i]&&!col[y][i]&&!arr[k][i]) 29 { 30 map[x][y] = i; 31 row[x][i] = 1; 32 col[y][i] = 1; 33 arr[k][i] = 1; 34 ++t; 35 if (dfs(keep[t][0],keep[t][1])) 36 return 1; 37 --t; 38 //回溯过程中，清除标记 39 map[x][y] = 0; 40 row[x][i] = 0; 41 col[y][i] = 0; 42 arr[k][i] = 0; 43 44 } 45 } 46 return 0; 47 48 } 49 int main() 50 { 51 int T; 52 scanf("%d",&T); 53 while(T--) 54 { 55 t = 0; 56 memset(row,0,sizeof(row)); 57 memset(col,0,sizeof(col)); 58 memset(arr,0,sizeof(arr)); 59 memset(keep,0,sizeof(keep)); 60 for (int i = 0;i < 9;i ++) 61 { 62 for (int j = 0;j < 9;j ++) 63 { 64 scanf("%1d",&map[i][j]);//控制格式输入 65 if (map[i][j]) 66 { 67 int k = i/3*3+j/3; 68 row[i][map[i][j]] = 1; 69 col[j][map[i][j]] = 1; 70 arr[k][map[i][j]] = 1; 71 } 72 else 73 { 74 keep[t][0] = i; 75 keep[t++][1] = j; 76 } 77 } 78 } 79 num = t; 80 t = 0; 81 dfs(keep[t][0],keep[t][1]); 82 } 83 return 0; 84 }
