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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' indicates a queen and '.' indicates an empty space.
A hard backtracking problem, graded against 6 test cases (3 of them hidden).
Systematic exploration of all candidates, abandoning partial ones that cannot work.
Reach for it when you see: "All permutations/combinations/subsets", or constraint puzzles like N-Queens and Sudoku.
More Backtracking problems →Place queens one row at a time. For each row, try every column. Use sets to track occupied columns, forward diagonals (row - col), and backward diagonals (row + col). If a placement is valid, recurse to the next row. When all rows are filled, save the board configuration.
The full reference solution in every supported language stays in the editor above - reveal it there once you have had a real attempt.
These apply to the pattern as a whole, not just this problem.