The Runtime Theory
mediumLeetCode#sorting#monotonic-stack

Car Fleet

Count groups of cars that reach a target together when faster cars cannot pass slower cars ahead.

The Runtime Theory Team25 min read
Solve it

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

Sample cases

intarget=12, position=[10,8,0,5,3], speed=[2,4,1,1,3]

out3

intarget=10, position=[3], speed=[3]

out1

intarget=100, position=[0,2,4], speed=[4,2,1]

out1

Count groups of cars that reach a target together when faster cars cannot pass slower cars ahead.

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

Sort cars from nearest to farthest and compare arrival times. A car joins the fleet ahead when its arrival time is no greater.

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 · stackDaily Temperaturesmedium · stackEvaluate Reverse Polish Notationmedium · stackGenerate Parentheses

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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