N-Queen.cpp

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

int board[20],count;

int main()
{
	int n,i,j;
	void queen(int row,int n);
	printf("\n\t --- N Queen Problem using Backtracking --- ");
	printf("\n\nEnter number of Queens: ");
	scanf("%d", &n);
	queen(1,n);
	return 0;
}

void print(int n)
{
	int i,j;
	printf("\n\nSolution %d:\n\n",++count);
	for(i=1;i<=n;++i)
		printf("\t%d",i);
	for(i=1;i<=n;++i)
	{
		printf("\n\n%d",i);
		for(j=1;j<=n;++j)
		{
			if(board[i]==j)
				printf("\tQ");
			else
				printf("\t-");
		}
	}
	printf("\n\n");
}

int place(int row,int column)
{
	int i;
	for(i=1;i<=row-1;++i)
	{
		if(board[i]==column)
			return 0;
		else
			if(abs(board[i]-column)==abs(i-row))
				return 0;
	}
	return 1;
}

void queen(int row,int n)
{
	int column;
	for(column=1;column<=n;++column)
	{
		if(place(row,column))
		{
			board[row]=column;
			if(row==n)
				print(n);
			else
				queen(row+1,n);
		}
	}
}