Backtracking

#include <iostream.h>

//Number of queens
int N;

//chessboard
int board[100][100];

//function to check if the cell is attacked or not
int is_attack(int i,int j)
{
    int k,l;
    //checking if there is a queen in row or column
    for(k=0;k<N;k++)
    {
        if((board[i][k] == 1) || (board[k][j] == 1))
            return 1;
    }
    //checking for diagonals
    for(k=0;k<N;k++)
    {
        for(l=0;l<N;l++)
        {
            if(((k+l) == (i+j)) || ((k-l) == (i-j)))
            {
                if(board[k][l] == 1)
                    return 1;
            }
        }
    }
    return 0;
}

int N_queen(int n)
{
    int i,j;
    //if n is 0, solution found
    if(n==0)
        return 1;
    for(i=0;i<N;i++)
    {
        for(j=0;j<N;j++)
        {
            //checking if we can place a queen here or not
            //queen will not be placed if the place is being attacked
            //or already occupied
            if((!is_attack(i,j)) && (board[i][j]!=1))
            {
                board[i][j] = 1;
                //recursion
                //wether we can put the next queen with this arrangment or not
                if(N_queen(n-1)==1)
                {
                    return 1;
                }
                board[i][j] = 0;
            }
        }
    }
    return 0;
}

int main()
{
    //taking the value of N
    cout<<"Enter the value of N for NxN chessboard\n";
    cin>>N;

    int i,j;
    //setting all elements to 0
    for(i=0;i<N;i++)
    {
        for(j=0;j<N;j++)
        {
            board[i][j]=0;
        }
    }
    //calling the function
    N_queen(N);
    //printing the matix
    for(i=0;i<N;i++)
    {
        for(j=0;j<N;j++)
            cout<<board[i][j]<<" ";
       cout<<"\n";
    }

}