Question

我试图找出我的代码出了什么问题，该代码应该可以解决9x9数独问题，当我使用sudoku的Wikipedia中的示例运行它时会崩溃。

我也尝试过使用递归，但是对它不是很熟悉，因此它也不起作用。

findunassignedlocation返回1，如果数字不存在，则返回0。
isSafe返回1，否则返回0。

如果问题可能出在其他功能之一，请告诉我，我将发送代码。忽略depth变量。

下面是我的代码：

/* Returns an int which indicates whether if the sudoku has any
   more empty entries (which shows as a 0) */
int FindUnassignedLocation(int grid[9][9]) { 
    for (int row = 0; row < 9; row++) 
        for (int col = 0; col < 9; col++) 
            if (grid[row][col] == 0) 
                return 1; 
    return 0; 
}

/* Returns an int which indicates whether an assigned entry 
   in the specified row matches the given number. */
int UsedInRow(int grid[9][9], int row, int num) { 
    for (int col = 0; col < 9; col++) 
        if (grid[row][col] == num) 
            return 1; 
    return 0; 
} 

/* Returns an int which indicates whether an assigned entry 
   in the specified column matches the given number. */
int UsedInCol(int grid[9][9], int col, int num) { 
    for (int row = 0; row < 9; row++) 
        if (grid[row][col] == num) 
            return 1; 
    return 0; 
} 

/* Returns an int which indicates whether an assigned entry 
   within the specified 3x3 box matches the given number. */
int UsedInBox(int grid[9][9], int boxStartRow, int boxStartCol, int num) { 
    for (int row = 0; row < 3; row++) 
        for (int col = 0; col < 3; col++) 
            if (grid[row + boxStartRow][col + boxStartCol] == num) 
                return 1; 
    return 0; 
} 

/* Returns an int which indicates whether it will be legal to assign 
   num to the given row,col location. */
int isSafe(int grid[9][9], int row, int col, int num) { 
    /* Check if 'num' is not already placed in current row, 
       current column and current 3x3 box */
    if (!UsedInRow(grid, row, num) && 
        !UsedInCol(grid, col, num) && 
        !UsedInBox(grid, row - row % 3, col - col % 3, num) && 
        grid[row][col] == 0) {
        return 1;
    } else {
        return 0;
    }
} 

void solve_sudoku(int sudoku[9][9]) {
    int row = 0;
    int col = 0;
    if (FindUnassignedLocation(sudoku) == 0) { //if sudoku is completely filled
        return;
    }
    for (int num = 1; num <= 9; num++) {
        if (isSafe(sudoku, row, col, num) == 1) {
            sudoku[row][col] = num;
            solve_sudoku(sudoku, depth);
            sudoku[row][col] = 0;
        }
    }
}

Answer 1

一种简单的方法（但由于对称/旋转而不是最有效的方法）是尝试所有尝试将数字1最多放置到9的连续位置（0,0 0,1 .. 0,8 1 ，0 ...）递归，每次将数字放在8,8上都是一个解决方案

只需少量代码即可删除无用的 FindUnassignedLocation 并添加递归

如果我用SZ替换9以便也能够搜索3、6或9的大小，然后添加解决方案的代码，则代码可以是：

#include <stdio.h>

// 3, 6 or 9
#define SZ 9

/* Returns an int which indicates whether an assigned entry 
   in the specified row matches the given number. */
int UsedInRow(int grid[][SZ], int row, int num) 
{ 
  for (int col = 0; col < SZ; col++)
    if (grid[row][col] == num) 
      return 1; 

  return 0; 
} 

/* Returns an int which indicates whether an assigned entry 
   in the specified column matches the given number. */
int UsedInCol(int grid[][SZ], int col, int num) 
{ 
  for (int row = 0; row < SZ; row++) 
    if (grid[row][col] == num) 
      return 1; 

  return 0; 
} 

/* Returns an int which indicates whether an assigned entry 
   within the specified 3x3 box matches the given number. */
int UsedInBox(int grid[][SZ], int boxStartRow, int boxStartCol, int num) { 
  for (int row = 0; row < 3; row++) 
    for (int col = 0; col < 3; col++) 
      if (grid[row + boxStartRow][col + boxStartCol] == num) 
        return 1; 

  return 0; 
} 


/* Returns an int which indicates whether it will be legal to assign 
   num to the given row,col location. */
int isSafe(int grid[][SZ], int row, int col, int num) 
{ 
  /* Check if 'num' is not already placed in current row, 
     current column and current 3x3 box */
  return (!UsedInRow(grid, row, num) && 
          !UsedInCol(grid, col, num) && 
          !UsedInBox(grid, row - row % 3, col - col % 3, num));
} 

/* print a solution */
void draw(int sudoku[][SZ])
{
  for (int row = 0; row != SZ; ++row) {
    for (int col = 0; col != SZ; ++col)
      printf("%d", sudoku[row][col]);
    putchar('\n');
  }
  putchar('\n');
}

void solve_sudoku(int sudoku[][SZ], int row, int col)
{
  for (int num = 1; num <= 9; num++) { //loop through numbers 1 to SZ
    if (isSafe(sudoku, row, col, num) == 1) { //the number is safe
      sudoku[row][col] = num;
      if ((col + 1) == SZ) {
        if ((row + 1) == SZ) {
          // done
          draw(sudoku);
        }
        else
          solve_sudoku(sudoku, row + 1, 0);
      }
      else
        solve_sudoku(sudoku, row, col + 1);
      sudoku[row][col] = 0;
    }
  }
}

int main()
{
  int sudoku[SZ][SZ] = {0};

  solve_sudoku(sudoku, 0, 0);
}

找到SZ 3的第一个解决方案（362880个可能的解决方案）：

找到SZ 6的第一个解决方案：

找到SZ 9的第一个解决方案

Sudoku求解器在C中崩溃

1 个答案: