#include <cstdio>
#include <cstdlib>
#include "sudoku.h"

Sudoku::Sudoku()
{
  int i, j;
  char c;

  for (i = 0; i < 9; i++) {
    for (j = 0; j < 9; j++) {
      if (!(cin >> c)) {
        cerr << "Bad Sudoku File -- not enough entries\n";
        exit(1);
      } 
      if (c == '-')
	Grid[i][j] = -1;
      else if (c >= '0' && c <= '9')
	Grid[i][j] = c - '0';
      else {
        cerr << "Bad Sudoku File -- entry: " << c << endl;
        exit(1);
      } 
    }
  }
  for (i = 0; i < 9; i++) {
    if (!Is_Row_Valid(i)) {
      cerr << "Bad Sudoku File -- Bad row " << i << endl;
      exit(1);
    }
    if (!Is_Col_Valid(i)) {
      cerr << "Bad Sudoku File -- Bad col " << i << endl;
      exit(1);
    }
  }
  for (i = 0; i < 9; i += 3) {
    for (j = 0; j < 9; j += 3) {
      if (!Is_Panel_Valid(i, j)) {
        cerr << "Bad Sudoku File -- Bad panel starting at row " << i << " col " << j << endl;
        exit(1);
      }
    }
  }
}

void Sudoku::Print_Screen()
{
  int i, j;

  for (i = 0; i < 9; i++) {
    for (j = 0; j < 9; j++) {
      if (j != 0) printf(" ");
      if (Grid[i][j] == -1)
	printf("- ");
      else
	printf("%d ", Grid[i][j]);
      if (j == 2 || j == 5) printf("  ");
    }
    printf("\n");
    if (i == 2 || i == 5) printf("\n");
  }
}

void Sudoku::Print_Convert()
{
}

bool Sudoku::Solve()
{
  return Recursive_Solve(0, 0);
}
bool Sudoku::Is_Row_Valid(int r)
{
  int i;

  for (i = 1; i <= 9; i++) checker[i] = false;

  for (i = 0; i < 9; i++) {
    if (Grid[r][i] != -1) {
      if (checker[Grid[r][i]]) return false;
      checker[Grid[r][i]] = true;
    }
  }
  return true;
}

bool Sudoku::Is_Col_Valid(int c)
{
  int i, j;
    
  for (i = 1; i <= 9; i++) checker[i] = false;

  for (i = 0; i < 9; i++) {
    if (Grid[i][c] != -1) {
      if (checker[Grid[i][c]]) return false;
      checker[Grid[i][c]] = true;
    }
  }
  return true;
}

bool Sudoku::Is_Panel_Valid(int sr, int sc)
{
  int r, c, i;
  for (i = 1; i <= 9; i++) checker[i] = false;

  for (r = sr; r < sr+3; r++) {
    for (c = sc; c < sc+3; c++) {
      if (Grid[r][c] != -1) {
        if (checker[Grid[r][c]]) return false;
        checker[Grid[r][c]] = true;
      }
    }
  }
  return true;
}

bool Sudoku::Recursive_Solve(int r, int c)
{
  int i;
  
  /* Skip all non-dash characters */
  while (r < 9 && Grid[r][c] != -1) {
    c++;
    if (c == 9) {
      r++;
      c = 0;
    }
  }

  /* Base case -- we're done */
  if (r == 9) return true;

  /* Try each value.  If successful, then return true. */
  for (i = 1; i <= 9; i++) {
    Grid[r][c] = i;
    if (Is_Row_Valid(r) && 
        Is_Col_Valid(c) && 
        Is_Panel_Valid(r-r%3, c-c%3) &&
        Recursive_Solve(r, c)) {
      return true;
    }
  }

  /* If unsuccessful, reset the element and return false. */
  
  Grid[r][c] = -1;
  return false;
}