diff --git a/Backtracking/NQueen.js b/Backtracking/NQueen.js
index dfd3dfa9fb..d76f232125 100644
--- a/Backtracking/NQueen.js
+++ b/Backtracking/NQueen.js
@@ -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]) {
@@ -25,18 +26,26 @@ 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)
}
}
@@ -44,22 +53,11 @@ class NQueen {
}
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 }
diff --git a/Backtracking/tests/NQueen.test.js b/Backtracking/tests/NQueen.test.js
new file mode 100644
index 0000000000..50000d1be1
--- /dev/null
+++ b/Backtracking/tests/NQueen.test.js
@@ -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)
+ })
+})
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