Backtracking on Jeanphilo Blog

LeetCode 78: Subsets, Derive the startIndex Backtracking Template

Sun, 03 May 2026 14:25:07 +0800

Problem Requirement

Input / Output

Input: nums, with 1 <= nums.length <= 10
Value range: -10 <= nums[i] <= 10
All elements in nums are distinct
Output: return all possible subsets of nums
Ordering: the result order does not matter, and subset element order is not the point

Example

Input: nums = [1,2,3]
Output: [[],[1],[2],[1,2],[3],[1,3],[2,3],[1,2,3]]

This tutorial builds one minimal Python solution.

Start From the Search Tree for `[1,2]`

The smallest branching example is:

LeetCode 90: Subsets II, Derive Layer-Level Deduplication

Sun, 03 May 2026 14:25:07 +0800

Problem Requirement

Input / Output

Input: nums, with 1 <= nums.length <= 10
Value range: -10 <= nums[i] <= 10
nums may contain duplicates
Output: return all unique subsets
Ordering: the result order does not matter, but the same value sequence may appear only once

Example

Input: nums = [1,2,2]
Output: [[],[1],[1,2],[1,2,2],[2],[2,2]]

This tutorial starts with a correct but wasteful version, then derives sorting plus layer-level deduplication.

Start From Duplicate Branches in `[1,2,2]`

The smallest example that exposes the issue is:

Hot100: N-Queens Incremental Build Tutorial

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A teaching-first incremental tutorial for LeetCode 51 that grows the N-Queens solution from a tiny example and a minimal DFS into column and diagonal state optimization.

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A practical guide to LeetCode 131 that builds string-partition backtracking from scratch and shows why a palindrome table makes the search cleaner and more reusable.

LeetCode 216: Combination Sum III (Backtracking / Fixed-Length Search ACERS Guide)

Fri, 17 Apr 2026 14:31:12 +0800

Learn LeetCode 216 by deriving fixed-length combination search, use-once recursion, and bounded 1..9 pruning from the problem itself.

LeetCode 40: Combination Sum II (Backtracking / Same-Layer Dedup ACERS Guide)

Fri, 17 Apr 2026 14:31:10 +0800

Learn LeetCode 40 by deriving same-layer duplicate skipping, use-once recursion, and sorted pruning from the problem itself.

Hot100: Combination Sum (Backtracking / Pruning ACERS Guide)

Wed, 08 Apr 2026 16:22:57 +0800

A practical guide to LeetCode 39 that builds combination backtracking from scratch, explains remain-based state, and shows why sorting makes pruning safe.

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A practical guide to LeetCode 46 covering used[] state tracking, leaf-only collection, and runnable multi-language implementations.

Backtracking on Jeanphilo Blog

LeetCode 78: Subsets, Derive the startIndex Backtracking Template

Problem Requirement

Input / Output

Example

Start From the Search Tree for [1,2]

LeetCode 90: Subsets II, Derive Layer-Level Deduplication

Problem Requirement

Input / Output

Example

Start From Duplicate Branches in [1,2,2]

Hot100: N-Queens Incremental Build Tutorial

Hot100: Palindrome Partitioning (Backtracking / Palindrome Table ACERS Guide)

LeetCode 216: Combination Sum III (Backtracking / Fixed-Length Search ACERS Guide)

LeetCode 40: Combination Sum II (Backtracking / Same-Layer Dedup ACERS Guide)

Hot100: Combination Sum (Backtracking / Pruning ACERS Guide)

Hot100: Permutations (used[] Backtracking ACERS Guide)

Start From the Search Tree for `[1,2]`

Start From Duplicate Branches in `[1,2,2]`