n_queens.js

function canBePlaced(board, x, y, n) {
  //rows above the current column
  for (let row = 0; row < y; row++) {
    if (board[row][x]) return false
  }

  let row = y;
  let col = x;
  // upper-left diagonal
  while (row >= 0 && col >= 0) {
    if (board[row][col]) return false
    row--
    col--
  }

  row = y;
  col = x;
  // upper-right diagonal
  while (row >= 0 && col < n) {
    if (board[row][col]) return false
    row--
    col++
  }

  return true
}

function solveQueens(board, y, n) {
  // base condition
  if (y >= n) return true;
  for (let col = 0; col < n; col++) {
    if (canBePlaced(board, col, y, n)) {
      board[y][col] = 1
      if (solveQueens(board, y + 1, n)) return true
      else board[y][col] = 0
    }
  }
  return false
}

function generateBoard(n) {
  let board = []
  for (let i = 0; i < n; i++) {
    board.push(new Array(n).fill(0))
  }
  return board
}

function main(n) {
  let board = generateBoard(n);
  console.log(solveQueens(board, 0, n))
  console.log(board)
}

main(30)