Hash Table

Problem Statement Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: Open brackets must be closed by the same type of brackets. Open brackets must be closed in the correct order. Every close bracket has a corresponding open bracket of the same type. Example 1: Input: s = "()" Output: true Example 2: Input: s = "()[]{}" Output: true Example 3: Input: s = "(]" Output: false Solution Intuition & Patterns Leetcode #20, Valid Parentheses, is a great introduction to LIFO (last in first out) stack problems....

Introduction After weeks of preparation, the big day has finally arrived. At 10:28 am PST, Javier (👨) is moments away from his first interview with Jordanna (👩), a senior software engineer at MAANG inc. The zoom call begins. 👩 “Thanks for taking the time to interview with us today. We’ll start off with brief introductions. My name is Jordanna and I earned my M.Sc. from UPenn before joining MAANG six years ago....

Problem Statement A transformation sequence from word beginWord to word endWord using a dictionary wordList is a sequence of words beginWord -> s1 -> s2 -> ... -> sk such that: Every adjacent pair of words differs by a single letter. Every si for 1 <= i <= k is in wordList. Note that beginWord does not need to be in wordList. sk == endWord Given two words, beginWord and endWord, and a dictionary wordList, return the number of words in the shortest transformation sequence from beginWord to endWord, or 0 if no such sequence exists....