The Runtime Theory
mediumLeetCode#backtracking#decision-tree

Subsets

Return every subset of a list of distinct values, including the empty and full subsets.

The Runtime Theory Team25 min read
Solve it

Solving happens on the judge — come back and mark it done

Sample cases

innums=[1,2,3]

out8 subsets

innums=[0]

out[[],[0]]

innums=[]

out[[]]

Return every subset of a list of distinct values, including the empty and full subsets.

A good solution should

  • State the invariant or decision rule that makes the approach correct.
  • Explain the time and space complexity in terms of the input sizes and required output.
  • Handle empty, minimal, duplicate, and boundary-shaped inputs covered by the contract.

Reasoning prompt

At each value, choose include or exclude. The output size is exponential, so state complexity in terms of both input and output.

Use the linked judge for the canonical problem. The examples above are compact TRT checks; write additional cases before submitting, especially for the boundary that tends to break your chosen invariant.

More practice in this topic

medium · backtrackingCombination Sum IImedium · backtrackingCombination Summedium · backtrackingLetter Combinations of a Phone Number

One dispatch a week

The trace behind each problem, the tradeoff that explains it, and one technical dispatch per week — no noise.

One technical dispatch per week. No noise.

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