[POJ2676 Sudoku]

[题目来源]：POJ2676

[关键字]：搜索

[题目大意]：完成一个数独（任意可行解）。

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[分析]：类似八皇后，只不过限制条件更多了，细心一点，注意一些技巧一次AC。对了，据说此题1 to 9循环比9 to 1循环，慢很多==

[代码]：

View Code

  1 program Project1;
  2 type
  3   rec = record
  4     x, y: longint;
  5   end;
  6 var
  7   map: array[0..10,0..10] of longint;
  8   a: array[0..90] of rec;
  9   line, row, quee: array[0..10,0..10] of boolean;
 10   tc, tot: longint;
 11   goal: boolean;
 12 
 13 function find(x, y: longint):longint;
 14 begin
 15   if ((1 <= x) and (x <= 3)) and ((1 <= y) and (y <= 3)) then exit(1);
 16   if ((1 <= x) and (x <= 3)) and ((4 <= y) and (y <= 6)) then exit(2);
 17   if ((1 <= x) and (x <= 3)) and ((7 <= y) and (y <= 9)) then exit(3);
 18   if ((4 <= x) and (x <= 6)) and ((1 <= y) and (y <= 3)) then exit(4);
 19   if ((4 <= x) and (x <= 6)) and ((4 <= y) and (y <= 6)) then exit(5);
 20   if ((4 <= x) and (x <= 6)) and ((7 <= y) and (y <= 9)) then exit(6);
 21   if ((7 <= x) and (x <= 9)) and ((1 <= y) and (y <= 3)) then exit(7);
 22   if ((7 <= x) and (x <= 9)) and ((4 <= y) and (y <= 6)) then exit(8);
 23   if ((7 <= x) and (x <= 9)) and ((7 <= y) and (y <= 9)) then exit(9);
 24 end;
 25 
 26 procedure init;
 27 var
 28   i, j, num, x: longint;
 29   ch: char;
 30 begin
 31   fillchar(line,sizeof(line),true);
 32   fillchar(row,sizeof(row),true);
 33   fillchar(quee,sizeof(quee),true);
 34   tot := 0;
 35   for i := 1 to 9 do
 36     begin
 37       for j := 1 to 9 do
 38         begin
 39           read(ch);
 40           x := ord(ch)-48;
 41           map[i,j] := x;
 42           if x = 0 then
 43             begin
 44               inc(tot);
 45               a[tot].x := i;
 46               a[tot].y := j;
 47             end;
 48           line[j,x] := false;
 49           row[i,x] := false;
 50           num := find(i,j);
 51           quee[num,x] := false;
 52         end;
 53         readln;
 54      end;
 55   {for i := 1 to 9 do
 56     for j := 1 to 9 do if not quee[i,j] then writeln(i,' ',j);}
 57 end;
 58 
 59 procedure dfs(k: longint);
 60 var
 61   i, x, y, num: longint;
 62 begin
 63   if k > tot then
 64     begin
 65       goal := true;
 66       exit;
 67     end;
 68   for i := 9 downto 1 do
 69     begin
 70       x := a[k].x;
 71       y := a[k].y;
 72       num := find(x,y);
 73       if (line[y,i]) and (row[x,i]) and (quee[num,i]) then
 74         begin
 75           map[x,y] := i;
 76           line[y,i] := false;
 77           row[x,i] := false;
 78           quee[num,i] := false;
 79           dfs(k+1);
 80           if goal then exit;
 81           line[y,i] := true;
 82           row[x,i] := true;
 83           quee[num,i] := true;
 84         end;
 85     end;
 86 end;
 87 
 88 procedure print;
 89 var
 90   i, j: longint;
 91 begin
 92   for i := 1 to 9 do
 93     begin
 94       for j := 1 to 9 do write(map[i,j]);
 95       writeln;
 96     end;
 97 end;
 98 
 99 begin
100   //assign(input,'d:\1.in');reset(input);
101   //assign(output,'d:\1.out');rewrite(output);
102   readln(tc);
103   while tc > 0 do
104     begin
105       init;
106       goal := false;
107       dfs(1);
108       print;
109       dec(tc);
110     end;
111   //close(input);
112   //close(output);
113 end.