LeetCode 394 — Decode String | Stack + Recursion Solution (MAANG / Google / Amazon Prep)

Published: 01 January 1970
on channel: Pen And Paper

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LeetCode 394 — Decode String | Stack + Recursion Solution (MAANG / Google / Amazon Prep)

In this video we tackle LeetCode 394: Decode String — a problem where you decode an encoded string like “3[a2[c]]” → “accaccacc”. We explore both recursion and stack-based approaches, so you can choose the one that best fits your coding interview style. Learn to handle nested encodings, integer parsing, brackets, and edge cases with depth.

What you will learn:

Problem statement and constraints: multiple nested brackets, multi-digit numbers, guarantee valid input.

Intuition behind recursion vs stack: when each shines, call stack vs explicit stack.

Step by step algorithm in Python and Java: parsing digits, pushing/popping characters, combining substrings.

Time and space complexity discussion (O(n × k) worst case, where k is max repeat), handling memory/stack depth.

Edge cases: empty strings, no repeated parts, large repeat counts, deep nesting.

Why this matters for MAANG / Google / Amazon interviews: tests parsing, stack/recursion, careful string handling — skills often tested in onsite or coding rounds.

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