Recursion & Backtracking

Debugger · v1.0

LIVE

1function solveNQUtil(col) {

2 // 1: Base Case

3 if (col >= N) return true;

5 // 2: Try placing queen in all rows one by one

6 for (let i = 0; i < N; i++) {

7 // 3: Check if queen can be placed here

8 if (isSafe(i, col)) {

10 // 4: Place queen

11 board[i][col] = QUEEN;

13 // 5: Recur for next columns

14 if (solveNQUtil(col + 1)) return true;

16 // 6: BACKTRACK - Remove Queen

17 board[i][col] = EMPTY;

18 }

19 }

20 // 7: Could not place return false

21 return false;

22}

Debugger · v1.0

LIVE

1function solveNQUtil(col) {

2 // 1: Base Case

3 if (col >= N) return true;

5 // 2: Try placing queen in all rows one by one

6 for (let i = 0; i < N; i++) {

7 // 3: Check if queen can be placed here

8 if (isSafe(i, col)) {

10 // 4: Place queen

11 board[i][col] = QUEEN;

13 // 5: Recur for next columns

14 if (solveNQUtil(col + 1)) return true;

16 // 6: BACKTRACK - Remove Queen

17 board[i][col] = EMPTY;

18 }

19 }

20 // 7: Could not place return false

21 return false;

22}

State Inspector

Variable	Value
$n	4

Board:4x4

Recursion & Backtracking

N-Queens Algorithm

Step 1 of 6

A classic combinatorial problem that demonstrates the power of recursive trial-and-error (Backtracking).

The Objective

Place N queens on an N×N board such that no two queens attack each other. This means no two queens can be in the same row, column, or diagonal.

Queen

Under Attack