Function nqueens

chapter08/8.12 - Eight Queens/nQueens.js:42–66

(n)

};

var nqueens = function(n) {
  var board = [];
  var checker = '';
  var answers = [];
  
  for (var i = 0; i < n; i++) {
    board.push(-1);
    checker += '0';
  }

  var recurse = function(currentBoard, center, leftDiag, rightDiag, currRow) {
    if (currRow === n) {
      answers.push(currentBoard);
    }
    for (var i = 0; i < n; i++) {
      if (center.charAt(i) === '0' && leftDiag.charAt(i) === '0' && rightDiag.charAt(i) === '0') {
        currentBoard[i] = currRow;
        recurse(currentBoard, changeChar(center, i, '1'), leftShift(changeChar(leftDiag, i, '1'), n), rightShift(changeChar(rightDiag, i, '1'), n), currRow + 1);
        currentBoard[i] = -1; // untoggle board to save on space complexity for arrays per recursive step
      }
    }
  };
  recurse(board, checker, checker, checker, 0);
  return answers;
};

/* TEST */
// leftShift works as expected