Leetcode-Medium

The reorderList function will return the head of the reordered linked list given a linked list as input

Reorder Linked Lists

Problem Statement We have to implement the reorderList function that takes the head node of a linked list as input and reorders its nodes in the format specified below. Given an input list like the following: $$Node_0 \rightarrow Node_1 \rightarrow Node_2 \rightarrow \dots \rightarrow Node_{(n-2)} \rightarrow Node_{(n-1)} \rightarrow Node_n$$ the reorderList function should reorder its nodes as: $$Node_0 \rightarrow Node_n \rightarrow Node_1 \rightarrow Node_{(n-1)} \rightarrow Node_2 \rightarrow Node_{(n-2)} \rightarrow \dots$$ ...

The longestConsecutive function will return the length of the longest sequence if consecutive numbers in the input array

Finding the Longest Consecutive Sequence in an Array

Problem Statement We have to implement the longestConsecutive function that takes an integer array as input and returns the length of the longest sequence of consecutive integers. For example, in array [4, 2, 7, 8, 1, 5, 6, 0] we have two sequences of consecutive integers: [0, 1, 2] and [4, 5, 6, 7, 8]. The longest sequence ([4, 5, 6, 7, 8]) has length 5. ...

The encode function will encode a list of strings to a single string while the decode function will take the encoded string and return the original list of strings as output

Encoding and Decoding Functions for Strings

Problem Statement We have to implement an encode function that takes a list of string values as input and returns a single encoded string that could be transmitted over a network. On the other side of the network, the decode function will take the encoded string as input and return the original list of string values as output. A delimiter could be used to differentiate between words. For example, ["Hello", "World"] could be encoded with comma delimiter (,) to "Hello,World". ...

The isValidSudoku function will return true if the input matrix represents a valid sudoku grid and false otherwise

Checking the Validity of a Sudoku Grid

Problem Statement We have to implement an isValidSudoku function that takes a 9x9 matrix (representing a Sudoku grid) as input and returns true if the grid is valid and false otherwise. Sudoku Grid A Sudoku grid is valid if Every row contains digits from 1 to 9 without repetition. Rows in a Sudoku Grid Every column contains digits from 1 to 9 without repetition. ...

The productExceptSelf function will returns an array of products of all the elements without the element at the same index in input array

Building a Product Array without the Element Itself

Problem Statement We have to implement a productExceptSelf function that takes an integer array nums as input and returns another array answer as output. The element answer[i] will be the product of all elements in inputArray except inputArray[i]. The implementation should not contain a division (/) operation because the answer array could also be created by iterating over all elements in inputArray and dividing them from the product of the complete array. ...

The topkFrequent function will return the top k most frequent elements in an array

Finding Most Frequent Elements in an Array

Problem Statement We have to implement a topKFrequent function that takes an integer array and a value k as input and returns the k most frequent elements in the input array. For example, topKFrequent({1, 1, 2, 2, 3, 5, 2}, 2) will return the top 2 most frequent elements in the array i.e. {2, 1}. If multiple elements have the same frequency, then any of them could be returned in the solution as long as its length is k. ...

The groupAnagrams function will return an array with anagrams grouped together

Group Anagrams in an Array

Problem Statement We have to implement a groupAnagram function that takes an array of strings as input and returns a new array with anagrams grouped. The input string array is assumed to be composed entirely of lowercase English characters. Brute Force Solution If two strings are anagrams then their sorted order will be the same. Thus, anagrams could be grouped under their sorted order. ...