From: David Tran <email55555@...>
Date: 2005-08-25T03:50:39+09:00
Subject: Re: [QUIZ] Sodoku Solver (#43)

The way I translate the Java's continue label is not "ruby way".

The java's continue label is like:

static void ShowAllAns() {
 for (int i = 0; i < 9; i++) {
   for (int j = 0; j < 9; j++) {
     if (puzzle[i][j] <= 0) {
       next_value: for (int value = 1; value <= 9; value++) {
         // On the same column, make sure no any row already used it
         // On the same row, make sure no any column already used it
         for (int k = 0; k < 9; k++) {
           if ((puzzle[k][j] == value) || (puzzle[i][k] == value)) {
             continue next_value;  // continue with label
           }
         }
         // On the 3x3 box, make sure no other cell already used it
         int p = (i / 3) * 3;
         int q = (j / 3) * 3;
         for (int x = 0; x < 3; x++) {
           for (int y = 0; y < 3; y++) {
             if (puzzle[p+x][q+y] == value) {
               continue next_value; // continue with label
             }
           }
         }

         puzzle[i][j] = value;
         ShowAllAns();
         puzzle[i][j] = 0;
       }
       return;  // tried all possible value, just return
     }
   }
 }
 PrintPuzzle();
}

----------------------------
I translated like :

  def solve
   9.times do |row|
     9.times do |col|
       next if @ary[row][col]

       # find next possible value for @ary[row][col]
       1.upto(9) do |v|
         # check on same row/col, no any col/row already used it
         next unless 9.times { |i| break if @ary[i][col] == v ||
@ary[row][i] ==v }

         # check on 3x3 box, no other cell already used it
         next unless 3.times do |i|
           break unless 3.times do |j|
             break if @ary[i + row / 3 * 3][j + col / 3 * 3] == v
           end
         end

         @ary[row][col] = v

         if solve
           return true
         else
           @ary[row][col] = nil  # backtracking
         end
       end

       return false
     end
   end
   true
 end

-------------------------------
Using too many breaks to simulate Java's continue label...
I almost forget Ruby's throw-catch.
I think translate Java's continue label the "Ruby" way maybe like this:

 def solve
   9.times do |row|
     9.times do |col|
       next if @ary[row][col]

       # find next possible value for @ary[row][col]
       1.upto(9) do |v|
         catch :next do
           # check on same row/col, no any col/row already used it
           9.times { |i| throw :next if @ary[i][col] == v || @ary[row][i] ==v }

           # check on 3x3 box, no other cell already used it
           3.times do |i|
             3.times do |j|
               throw :next if @ary[i + row / 3 * 3][j + col / 3 * 3] == v
             end
           end

           @ary[row][col] = v

           if solve
             return true
           else
             @ary[row][col] = nil  # backtracking
           end
         end
       end
       return false
     end
   end
   true
 end