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Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure...

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A sentence is a string of single-space separated words where each word can contain digits, lowercase letters, and the dollar sign '$'. A word represents a price if it is a sequence of digits preceded by a dollar sign...

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Given a string s, sort it in decreasing order based on the frequency of the characters. The frequency of a character is the number of times it appears in the string...

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An interesting problem on leetcode to find minimum number of ways to pick up consecutive cards. We will start with a brute force algorithm that would exceed in time limit. Later we will improve upon this algorithm using hashmap...

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You are given a **0-indexed** binary array `nums` of length `n`. `nums` can be divided at index `i` (where `0 <= i <= n`) into two arrays (possibly empty) nums_{left} and nums_{right}..

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There are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1. You are given an array prerequisites where prerequisites[i] = [a_{i}, b_{i}] indicates that you must take course b_{i} first if you want to take course a_{i}...

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You are given a string s and an integer k, a k duplicate removal consists of choosing k adjacent and equal letters from s and removing them, causing the left and the right side of the deleted substring to concatenate together...

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Questions involving the binary tree data structure are very popular in tech interviews, and can be challenging and varied! A binary tree is a data structure consisting of a collection of nodes (starting at a root node), where each node consists of a value (data), together with a directed edges to at most two nodes (the "left child" and "right child"), with the additional conditions that no two edges point to the same node and no edge points to the root. I recently solved an interesting problem on binary tree...

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Ternary string is an interesting problem that could be solved using two pointers techniques. It's a convenient way to keep track of multiple indices. This helps in making decisions based on two values...

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It's one of the most popular questions on leetcode that seems very easy at first. Coin change is a classic dynamic programming problem. I will proceed with an obvious (albeit wrong) solution and subsequently proceed to an efficient correct solution...

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There's an interesting problem I recently solved on leetcode based on dynamic programming. My Github repository contains list of all problems that I have solved. I often start with a brute force approach without fretting about time complexity. Later I try to improve my algorithm for a better efficient solution...

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Graph are data structures made of vertices & edges. There are lots of interesting problems that can be solved using graphs. Part 1 covers the basic for creating a template for graph data structure...

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I recently came across a simple telephonic interview problem. The problem was to sort an array recursively. But even numbers need to be placed before odd numbers. At first glance it was obvious that it was a simple case of implementation of merge sort...

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Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero...

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