NQueens.js

class NQueens {
 constructor(size) {
 if (size < 0) {
 throw RangeError('Invalid board size')
 }
 this.board = new Array(size).fill('.').map(() => new Array(size).fill('.'))
 this.size = size
 this.solutionCount = 0
 }

 isValid([row, col]) {
 // function to check if the placement of the queen in the given location is valid

 // checking the left of the current row
 for (let i = 0; i < col; i++) {
 if (this.board[row][i] === 'Q') return false
 }

 // checking the upper left diagonal
 for (let i = row, j = col; i >= 0 && j >= 0; i--, j--) {
 if (this.board[i][j] === 'Q') return false
 }

 // checking the lower left diagonal
 for (let i = row, j = col; j >= 0 && i < this.size; i++, j--) {
 if (this.board[i][j] === 'Q') return false
 }

 return true
 }

 placeQueen(row, col) {
 this.board[row][col] = 'Q'
 }

 removeQueen(row, col) {
 this.board[row][col] = '.'
 }

 solve(col = 0) {
 if (col >= this.size) {
 this.solutionCount++
 return true
 }

 for (let i = 0; i < this.size; i++) {
 if (this.isValid([i, col])) {
 this.placeQueen(i, col)
 this.solve(col + 1)
 this.removeQueen(i, col)
 }
 }

 return false
 }

 printBoard(output = (value) => console.log(value)) {
 if (!output._isMockFunction) {
 output('\n')
 }
 for (const row of this.board) {
 output(row)
 }
 }
}

export { NQueens }