Subsets II

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Problem

Given an integer array that may contain duplicates, return all possible unique subsets (the power set), without duplicate subsets.

Examples

Example 1

Input:nums = [1,2,2]

Output:[[],[1],[1,2],[1,2,2],[2],[2,2]]

Constraints

1 <= nums.length <= 10

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How to approach it: the Backtracking pattern

Explore a decision one choice at a time, undo it if it doesn't lead anywhere, and try the next option. It's a systematic way to generate every valid combination, permutation, or arrangement.

Look for this pattern when

The problem asks for "all possible" combinations, subsets, permutations, or valid arrangements.
A greedy or direct-formula approach doesn't work because you genuinely need to explore multiple branches.

Read the full Backtracking guide →

Video walkthroughs

Original problem on LeetCode ↗