Nqueens.java

public class Nqueens {
    public static boolean issafe(char board[][], int row, int col){
        //vertical up
        for (int i = row-1; i >= 0; i--) {
            if(board[i][col]=='Q'){
                return false;
            }
        }
        //diag left up
        for (int i = row-1, j=col-1; i>=0 && j>=0; i--,j--){
            if(board[i][j]=='Q'){
                return false;
            }
        }
  //diag right up
  for (int i = row-1, j=col+1; i>=0 && j<board.length; i--,j++){
    if(board[i][j]=='Q'){
        return false;
    }
}
return true;
    }
    public static void nQueens(char board[][], int row){
        //base
        if(row == board.length){
            printBoard(board);
           // count++;
            return;
        }
        for(int j = 0;j<board.length;j++){
            if(issafe(board,row,j)){
            board[row][j]='Q';
            nQueens(board, row+1);
            board[row][j] = 'x';
            }
        }
    }
    public static void printBoard(char board[][]){
        System.out.println("-------chese board-------");
        for(int i = 0; i<board.length;i++){
            for(int j = 0; j<board.length;j++){
                System.out.print(board[i][j]+" ");
            }
            System.out.println();
        }
    }
    static int count = 0;
    public static void main(String[] args) {
        int n = 5;
        char board[][] = new char[n][n];
        //intialize
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
               board[i][j]  = 'x';   
            }
            
        }
        nQueens(board,0);
       // System.out.println("total ways to solve n queens = " + count);
    }
    
}