N queens

NQ.js

/*
Eight Queens:Write an algorithm to print all ways of arranging eight queens on an 8x8 chess board
so that none of them share the same row, column, or diagonal. In this case, "diagonal" means all
diagonals, not just the two that bisect the board.
*/

var GRID_SIZE = 4;


function check(board, r1, c1) {
  for(var r2 = 0; r2 < r1; r2++) {
     var c2 = board[r2];
    if(c2 === c1) {
      return false;
    }
    if((r1 - r2) === Math.abs(c1 - c2)) {
      return false
    }
  }
  return true;
}


function NQ(r, board = [], results = []) {
  if(r === GRID_SIZE) {
    results.push([...board]);
    board = [];
  }
  for(var c = 0; c < GRID_SIZE; c++) {
    if(check(board, r, c)) {
      board[r] = c;
      NQ(r+1, board, results);
    }
  }
}
var results = [];
NQ(0, [], results);

console.log('results', results);