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Merged
raklaptudirm merged 1 commit into from
Jun 7, 2021
Merged

Find all the solutions of NQueen #619

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40 changes: 19 additions & 21 deletions Backtracking/NQueen.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ class NQueen {
constructor (size) {
this.board = new Array(size).fill('.').map(() => new Array(size).fill('.'))
this.size = size
this.solutionCount = 0
}

isValid ([row, col]) {
Expand All @@ -25,41 +26,38 @@ class NQueen {
return true
}

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

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

solve (col = 0) {
// function to solve the board
if (col >= this.size) { return true }
if (col >= this.size) {
this.printBoard()
this.solutionCount++
return true
}

for (let i = 0; i < this.size; i++) {
if (this.isValid([i, col])) {
this.board[i][col] = 'Q'

if (this.solve(col + 1)) { return true }

// backtracking
this.board[i][col] = '.'
this.placeQueen(i, col)
this.solve(col + 1)
this.removeQueen(i, col)
}
}

return false
}

printBoard () {
// utility function to display the board
console.log('\n')
for (const row of this.board) {
console.log(...row)
}
}
}

function main () {
const board = new NQueen(8)

board.printBoard()
console.log('\n')

board.solve()

board.printBoard()
}

main()
export { NQueen }
15 changes: 15 additions & 0 deletions Backtracking/tests/NQueen.test.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
import { NQueen } from '../NQueen'

describe('NQueen', () => {
it('should return 2 solutions for 4x4 size board', () => {
const _4Queen = new NQueen(4)
_4Queen.solve()
expect(_4Queen.solutionCount).toEqual(2)
})

it('should return 92 solutions for 8x8 size board', () => {
const _8Queen = new NQueen(8)
_8Queen.solve()
expect(_8Queen.solutionCount).toEqual(92)
})
})