Freaks City

Problem Description Given a list of accounts where each account is represented as a list of strings, the first element being a name and the remaining elements being email addresses associated with that account. The task is to merge these accounts based on shared email addresses. If two accounts have at least one email in common, they belong to ...

Binary tree traversal is a fundamental operation in computer science, visiting each node in the tree in a specific order. This article covers four essential traversal methods with both recursive and iterative implementations. Preorder Traversal (Root-Left-Right) Preorder traversal visits the root node first, then the left subtree, followed by t ...

Two Sum Given an array of integers nums and a target value target, find the indices of two numbers that add up to target. Return the indices as a pair. Solution 1: Brute Force class Solution { public int[] twoSum(int[] nums, int target) { for (int i = 0; i < nums.length; i++) { for (int j = i + 1; j < nums.lengt ...

get(index): Get the value of the index-th node in the linked list. If the index is invalid, return -1. addAtHead(val): Add a node of value val before the first element of the linked list. After the insertion, the new node will be the first node of the linked list. addAtTail(val): Append a node of value val as the last element of the linked lis ...

Overview of Backtracking Backtracking is a systematic way to explore all potential solutions by building combinations incrementally and backtracking when a path fails to meet constraints. It's particularly useful for problems like combinations, permutations, subsets, and other combinatorial searches. Common problem types solved with backtrackin ...

Merge two ascending sorted linked lists into a new sorted linked list. The new list is constructed by splicing together all nodes from the two input linked lists. Example 1: Input: l1 = [1,2,4], l2 = [1,3,4] Output: [1,1,2,3,4,4] Example 2: Input: l1 = [], l2 = [0] Output: [0] class Solution: def mergeTwoLists(self, list1: ListNode, list ...

LeetCode 92. Reverse Linked List II Problem Statement Given the head of a singly linked list and two integers left and right where left <= right, reverse the nodes from position left to position right and return the modified list. Solution Strategy A stack provides an elegant mechanism to reverse elements in-place without complex pointer man ...

Problem Description: There are n teams numbered from 0 to n - 1 in a tournament. You are given a 0-indexed 2D boolean matrix grid of size n * n. For all i, j such that 0 <= i, j <= n - 1 and i != j, if grid[i][j] == 1, then team i is stronger than team j; otherwise, team j is stronger than team i. If there is no team that is stronger than ...

Implementing strStr() with the KMP Algorithm Given a haystack string and a needle string, locate the index of the first occurrence of the needle. The Knuth–Morris–Pratt (KMP) algorithm avoids redundant comparisons by precomputing a prefix table (often called the LPS – Longest Proper Prefix which is also Suffix – array). First, construct the LPS ...

Problem Description Given a string s and an integer array spaces, you need to insert a space before the character at each index specified in the spaces array. The spaces array is sorted in strictly increasing order, and all indices are valid (within the bounds of the string). Return the modified string after inserting the spaces. Examples Examp ...