The Runtime Theory
mediumLeetCode#hash-map#canonical-key

Group Anagrams

Group words that contain identical character counts; output group order may be arbitrary.

The Runtime Theory Team25 min read
Solve it

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

Sample cases

instrs=["eat","tea","tan","ate","nat","bat"]

out[["eat","tea","ate"],["tan","nat"],["bat"]]

instrs=[""]

out[[""]]

instrs=["a"]

out[["a"]]

Group words that contain identical character counts; output group order may be arbitrary.

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

Compare sorting each word to building a frequency signature. Include empty strings and repeated letters.

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

easy · arraysContains Duplicatemedium · arraysEncode and Decode a List of Stringsmedium · arraysLongest Consecutive Sequence

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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