Semi-Team

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Semi-Team

Team Members

1. Michael Fainshtein, Research, Development, Presentation

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Assignment 1

Rules to play Sudoku

Sudoku is a logic puzzle where a grid composed of mini grids is presented to the player to fill each cell with a number unique to its column, row and mini-grid.

Sudoku Backtrack Algorithm

 Find row, col of an unassigned cell
 If there is none, return true
 For digits from 1 to 9
   a) If there is no conflict for digit at row,col
       assign digit to row,col and recursively try fill in rest of grid
   b) If recursion successful, return true
   c) Else, remove digit and try another
 If all digits have been tried and nothing worked, return false

Sudoku Backtrack Function

  /* Takes a partially filled-in grid and attempts to assign values to
  all unassigned locations in such a way to meet the requirements
  for Sudoku solution (non-duplication across rows, columns, and boxes) */
  bool SolveSudoku(int grid[N])
  {
     int row, col;
     // If there is no unassigned location, we are done
     if (!FindUnassignedLocation(grid, row, col))
        return true; // success!
     // consider digits 1 to 16
     for (int num = 1; num <= n; num++)
     {
        // if looks promising
        if (isSafe(grid, row, col, num))
        {
           // make tentative assignment
           grid[(row)+(col*n)] = num;
           // return, if success, yay!
           if (SolveSudoku(grid))
              return true;
           // failure, unmake & try again
           grid[(row)+(col*n)] = UNASSIGNED;
        }
     }
     return false; // this triggers backtracking
  }

Source

http://www.geeksforgeeks.org/backtracking-set-7-suduku/