From 0b253baa40a7bbccdffd4dbebc0e68761a2b1626 Mon Sep 17 00:00:00 2001
From: Satyam Singh <111181853+Satyam-Singh-01@users.noreply.github.com>
Date: Sun, 5 Oct 2025 01:39:22 +0530
Subject: [PATCH] Create N-Queens

The n-queens puzzle is the problem of placing n queens on an n x n chessboard such that no two queens attack each other.

Given an integer n, return all distinct solutions to the n-queens puzzle. You may return the answer in any order.

Each solution contains a distinct board configuration of the n-queens' placement, where 'Q' and '.' both indicate a queen and an empty space, respectively.
---
 LeetCode/Problems/Python/N-Queens | 33 +++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 LeetCode/Problems/Python/N-Queens

diff --git a/LeetCode/Problems/Python/N-Queens b/LeetCode/Problems/Python/N-Queens
new file mode 100644
index 00000000..b6a57981
--- /dev/null
+++ b/LeetCode/Problems/Python/N-Queens
@@ -0,0 +1,33 @@
+class Solution:
+    def solveNQueens(self, n: int) -> List[List[str]]:
+        
+        if n == 0: return []
+        
+        col = set()
+        diagonal = set()    # determined by r+c
+        antidiagonal = set() #
+        output = []
+        result = []
+        
+        def backtrack(r):
+            nonlocal n,col,diagonal,antidiagonal,output,result
+            if r == n:
+                result.append(output[:])
+                return
+            
+            for c in range(n):
+                if c in col or (r+c) in diagonal or (r-c) in antidiagonal: continue
+                
+                col.add(c)
+                diagonal.add(r+c)
+                antidiagonal.add(r-c)
+                output.append('.'*c + 'Q' + '.'*(n-c-1))
+                backtrack(r+1)
+                
+                col.remove(c)
+                diagonal.remove(r+c)
+                antidiagonal.remove(r-c)
+                output.pop()
+        
+        backtrack(0)
+        return result