Documentation Index
Fetch the complete documentation index at: /llms.txt
Use this file to discover all available pages before exploring further.
Tested Python solution for LeetCode 52 with 11 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 52 # by problem number
lcpy gen -s n_queens_ii # by problem name
n queens on an n x n chessboard such that no two queens attack each other.
Given an integer n, return the number of distinct solutions to the n-queens puzzle.
Input: n = 4
Output: 2
Explanation: There are two distinct solutions to the 4-queens puzzle as shown.
Input: n = 1
Output: 1
1 <= n <= 9class Solution:
# Time: O(n!)
# Space: O(n)
def total_n_queens(self, n: int) -> int:
cols: set[int] = set()
diag1: set[int] = set()
diag2: set[int] = set()
def backtrack(row: int) -> int:
if row == n:
return 1
count = 0
for col in range(n):
if col in cols or (row - col) in diag1 or (row + col) in diag2:
continue
cols.add(col)
diag1.add(row - col)
diag2.add(row + col)
count += backtrack(row + 1)
cols.remove(col)
diag1.remove(row - col)
diag2.remove(row + col)
return count
return backtrack(0)
| Time | Space |
|---|---|
| O(n!) | O(n) |