n = 1
Input
1
Output
[['Q']]
Only one cell and one queen — the single solution is a board with 'Q'.
Full lesson preview
Solve the N-Queens problem
Place N queens on an N×N board so that no two queens attack each other.
Python practice28 minRecursion & BacktrackingAdvancedLast updated March 27, 2026
Problem statement
Given an integer n, return all distinct solutions to the n-queens puzzle. Each solution contains a distinct board configuration of the n-queens' placement, where 'Q' indicates a queen and '.' indicates an empty space. Represent each board as a list of n strings of length n. Return the list of solutions sorted lexicographically by the concatenation of their rows (so results are deterministic).
Task
Use backtracking to generate all distinct N-Queens solutions and return them in a consistent, sorted ordering.
Examples
Input format
A single integer n.
Output format
A list of solutions. Each solution is a list of n strings representing the board. The outer list must be sorted for determinism.
Constraints
1 <= n <= 10. Solutions must not place any two queens in the same row, column, or diagonal.
Samples
Sample 1
Input
4
Output
[['..Q.', 'Q...', '...Q', '.Q..'], ['.Q..', '...Q', 'Q...', '..Q.']]
Two distinct 4x4 solutions. The returned list is sorted lexicographically.