Invert Binary TreeQuestion: Invert a binary tree. Input: 4 / \ 2 7 / \ / \ 1 3 6 9 Output: 4 / \ 7 2 / \ / \ 9 6 3 1 Solution Approach 1: Recursive The inverse of an emp…

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Divisor GameAlice and Bob take turns playing a game, with Alice starting first. Initially, there is a number N on the chalkboard. On each player's turn, that playe…

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Single NumberQuestion: Given a non-empty array of integers nums, every element appears twice except for one. Find that single one. Solution Approach 1: Hash Table W…

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Smallest RangeGiven an array A of integers, for each integer A[i] we may choose any x with -K <= x <= K, and add x to A[i]. After this process, we have some array B.…

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Find the Distance Value Between Two ArraysLessons Learned: TreeSet, Array Manipulation

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Valid ParenthesesQuestion: Implement an algorithm to print all valid (properly opened and closed) combinations of n pairs of parentheses.

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Median of Two Sorted ArraysLessons Learned: Array parsing

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Word LadderThe problem: Given two words (start and end), and a dictionary, find the length of shortest transformation sequence from start to end.

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Word BreakQuestion: Given a string s and a dictionary of words dict, determine if s can be segmented into a space-separated sequence of one or more dictionary wo…

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Longest Palindromic Substring👋 Hello! I’m gathering feedback on SWE Prep. If you like to provide suggestions or feedback, let us know on this survey here! Question: Given a string…

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