The Runtime Theory
mediumLeetCode#strings#normalization

Reverse Words in a String

Reverse word order, remove leading and trailing spaces, and collapse repeated spaces to one.

The Runtime Theory Team25 min read
Solve it

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

Sample cases

ins="the sky is blue"

out"blue is sky the"

ins=" hello world "

out"world hello"

ins="a"

out"a"

Reverse word order, remove leading and trailing spaces, and collapse repeated spaces to one.

A good solution should

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

Reasoning prompt

Separate tokenization from ordering. Consider whether your language’s split behavior already collapses all whitespace in the required way.

Use the linked judge for the canonical challenge. The examples above are compact TRT checks; create additional tests around the boundary most likely to break your invariant.

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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