nQueen_Code.cpp

// here is the code for the n-queen pattern of nXn board.
#include <iostream>
using namespace std;

bool canPlace(int board[][20],int n,int x,int y){

    //Column
    for(int k=0;k<x;k++){
        if(board[k][y]==1){
            return false;
        }
    }
    //Left Diag 
    int i = x;
    int j = y;
    while(i>=0 and j>=0){
        if(board[i][j]==1){
            return false;
        }
        i--; j--;
    }

    //Right Diag
    i = x;
    j = y;
    while(i>=0 and j<n){
        if(board[i][j]==1){
            return false;
        }
        i--; j++;
    }
    return true;
}

void printBoard(int n,int board[][20]){

    for(int i=0;i<n;i++){
        for(int j=0;j<n;j++){
            cout<< board[i][j]<<" ";
        }
        cout<<endl;
    }
    cout <<endl;
}

bool solveNQueen(int n,int board[][20],int i){
    //base case 
    if(i==n){
        //Print the board
        printBoard(n,board);
        return true;
    }


    // rec case
    // try to place a queen in every row
    for(int j=0;j<n;j++){
        //whether the current i,j is safe or not 
        if(canPlace(board,n,i,j)){
            board[i][j] = 1;
            bool success = solveNQueen(n,board,i+1);
            if(success){
                return true;
            }
            //backtrack
            board[i][j] = 0;
        }
    }
    return false;
}

int main() {
    system("CLS");
    int board[20][20] = {0};
    int n;
    cin>>n;

    solveNQueen(n,board,0);

	return 0;
}