Longest Substring Of All Vowels in Order

Medium · sliding window solution for Longest Substring Of All Vowels in Order. Python, Go, and a step-by-step animation.

Problem

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

LeetCode 1839. Longest Substring Of All Vowels in Order. The copyrighted prompt is on LeetCode. This page is a working sliding window 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

s =: abcabcbb

Output

The longest unique window is abc (length 3).

Solution

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

Approach 1Optimal▶ Animated

Longest Substring Of All Vowels in Order — sliding window

Grow right, shrink left the moment the window breaks its invariant. Built for LeetCode 1839. Longest Substring Of All Vowels in Order.

The window [left, right] is the longest suffix ending at right that still obeys the rule (here: all unique). Last-seen indices tell you exactly how far to jump left.

Algorithm

Walk right across the string.
If s[right] was already inside the window, jump left past its last index.
Record the last-seen index and update the best length.

Time: O(n)
Space: O(σ)

Solution.py

1class Solution:2    def longestSubstringOfAllVowelsInOrder(self, s: str) -> int:3        last: dict[str, int] = {}4        left = 05        best = 06        for right, ch in enumerate(s):7            if ch in last and last[ch] >= left:8                left = last[ch] + 19            last[ch] = right10            best = max(best, right - left + 1)11        return best

Watch this run

Interactive walkthrough

Playing “Longest Substring Of All Vowels in Order — sliding window”. Edit the input, hit Run, then scrub.

Approach: Longest Substring Of All Vowels in Order — sliding window

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