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LEETFLIX

Count Commas in Range II

MediumMath
Solve on LeetCode

Medium · linear scan solution for Count Commas in Range II. Python, Go, and a step-by-step animation.

01

Problem

Read the prompt, flip through the examples, then steal the idea.

LeetCode 3871. Count Commas in Range II. The copyrighted prompt is on LeetCode. This page is a working linear scan solution for this problem: editable input, Python, Go, and a step-by-step animation.

Constraints

  • —Player inputs are capped so the animation stays readable.
  • —Match LeetCode's own constraints when you submit there.

Examples

Input

nums =
[2, 1, 5, 3]

Output

5

A single pass keeps the running maximum. 5 wins.

02

Solution

Python and Go. The walkthrough below runs this same code.

Approach 1Optimal▶ Animated

Count Commas in Range II — linear scan

Keep a running answer while you walk the array once. Built for LeetCode 3871. Count Commas in Range II.

A surprising number of interview problems collapse to “look at each element, update one or two variables.” Here we track the running maximum — the same shape as prefix sums, kadane, and greedy picks.

Algorithm

  1. Seed best with the first element.
  2. For each later x, set best = max(best, x).
  3. Return best.
Time
O(n)
Space
O(1)
Solution.py
class Solution:    def countCommasInRangeIi(self, nums: list[int]) -> int:        best = nums[0]        for x in nums[1:]:            if x > best:                best = x        return best
Watch this run

03

Interactive walkthrough

Playing “Count Commas in Range II — linear scan”. Edit the input, hit Run, then scrub.

Approach: Count Commas in Range II — linear scan

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