C code for solving sudoku recursively

recursive_sudoku.c

#include <stdlib.h>
#include <stdio.h>

int solve(int i, int j);
int recursiverowcheck(int i, int j, int n);
int recursivecollumncheck(int i, int j, int n);
int recursiveboxcheck(int i, int j, int n);
void printpuzzle(void);

/*
int sudoku[9][9] = {
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0 }
}*/

int sudoku[9][9] = {
	{ 2, 0, 0, 5, 0, 3, 0, 0, 8 },
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
	{ 0, 1, 4, 0, 0, 0, 6, 7, 0 },
	{ 0, 3, 0, 1, 0, 7, 0, 9, 0 },
	{ 0, 5, 0, 0, 9, 0, 0, 6, 0 },
	{ 0, 8, 0, 4, 0, 6, 0, 1, 0 },
	{ 0, 9, 1, 0, 0, 0, 2, 8, 0 },
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
	{ 5, 0, 0, 7, 0, 2, 0, 0, 6 }
};


void main()
{
	/*int sudoku[9][9] = {
		{ 2, 0, 0, 5, 0, 3, 0, 0, 8 },
		{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
		{ 0, 1, 4, 0, 0, 0, 6, 7, 0 },
		{ 0, 3, 0, 1, 0, 7, 0, 9, 0 },
		{ 0, 5, 0, 0, 9, 0, 0, 6, 0 },
		{ 0, 8, 0, 4, 0, 6, 0, 1, 0 },
		{ 0, 9, 1, 0, 0, 0, 2, 8, 0 },
		{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
		{ 5, 0, 0, 7, 0, 2, 0, 0, 6 }
	};

	int randomarray[9] = { 3, 5, 2, 6, 7, 8, 1, 9, 4 };
	

	int arr[9][9] = {
		{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
		{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
		{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
		{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
		{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
		{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
		{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
		{ 0, 0, 0, 0, 0, 0, 0, 0, 0 },
		{ 0, 0, 0, 0, 0, 0, 0, 0, 0 }
	};*/

	int i = 0, j = 0;
	int q=solve(i, j);
	printpuzzle();
	system("pause");		
}

int solve(int i, int j)
{
	int permanent = 0;
	if (sudoku[i][j] != 0)
	{
		permanent = 1;	
	}
	if (permanent == 1)
	{
		if (i == 8 && j == 8)
		{
			return 1;
		}
		else
		{
			if (j == 8)
			{
				if (solve(i + 1, 0) == 1)
				{
					return 1;
				}
				return 0;
			}
			else
			{
				if (solve(i, j + 1) == 1)
				{
					return 1;
				}
				return 0;
			}
		}
	}

		for (int n = 1; n < 10; n++)
		{
			if ((recursiveboxcheck(i, j, n) == 0 && recursivecollumncheck(i, j, n) == 0 && recursiverowcheck(i, j, n) == 0))
			{
				if (permanent==0)
					sudoku[i][ j] = n;
				if (i==8 && j==8)
				{
					return 1;
				}
				else
				{
					if (j == 8)
					{
						if (solve(i+1, 0) == 1)
						{
							return 1;
						}
					}
					else
					{
						if (solve(i, j+1) == 1)
						{
							return 1;
						}
					}
				}	
			}
		}
		if (permanent == 0)
			sudoku[i][j] = 0;
		return 0;
}

int recursiverowcheck(int i, int j, int n)
{
	for (int l = 0; l < 9; l++)
	{
		if (sudoku[i][l] == n)
		{
			return 1;
		}
	}
	return 0;
}
int recursivecollumncheck(int i, int j, int n)
{
	for (int l = 0; l < 9; l++)
	{
		if (sudoku[l][j] == n)
		{
			return 1;
		}
	}
	return 0;
}
int recursiveboxcheck(int i, int j, int n)
{
	for (int boxrow = (i / 3) * 3, rmax = boxrow + 3; boxrow < rmax; boxrow++)
	{
		for (int boxcollumn = (j / 3) * 3, cmax = boxcollumn + 3; boxcollumn < cmax; boxcollumn++)
		{
			if (sudoku[boxrow][boxcollumn] == n)
			{
				return 1;
			}
		}
	}
	return 0;
}

void printpuzzle(void)
{
	for (int i = 0; i < 9; i++)
	{
		for (int j = 0; j < 9; j++)
		{
			printf("%d", sudoku[i][j]);
		}
		printf("\n");
	}
}