Minimum Length After Removing Equal 'a' & 'b' Substrings — Math Insight Explained | LeetCode #3746

Welcome back! In this video we solve LeetCode Problem #3746 — Minimum String Length After Removing Equal A and B Substrings, a deceptively clever problem that looks like a complex simulation but collapses into a beautiful math insight once you think about it the right way.

The problem gives us a string made only of 'a' and 'b'. We can repeatedly remove any substring where the count of 'a' equals the count of 'b'. After each removal the string is concatenated back together, and we keep going until no more valid removals are possible. We need to return the minimum possible length of the final string.

The naive simulation approach — actually finding and removing substrings repeatedly — is complex to implement and expensive to run. Most people get stuck trying to simulate the process. But the key insight is that we never need to simulate at all.

Here's the mathematical truth behind this problem: every time we remove a substring with equal 'a' and 'b' counts, we're removing the same number of 'a's and 'b's from the string. The order doesn't matter — because after concatenation, we can always find new valid substrings. This means we can always keep removing as long as there are both 'a's and 'b's available to pair up. Each removal eliminates equal counts of both characters.
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Видео Minimum Length After Removing Equal 'a' & 'b' Substrings — Math Insight Explained | LeetCode #3746 канала Krishna