4Sum II: Pair Summation with Hash Maps Given four integer arrays of equal length, determine the number of tuple combinations (i, j, k, l) where the sum of corresponding elements equals zero. Unlike single-array k-sum problems requiring deduplication, this scenario involves four independent collectio...
Problem Description Given two non-empty linked lists representing non-negative integres in reverse digit order, combine the numbers and return the result as a linked list. Basic Iterative Approach class Solution { public ListNode addTwoNumbers(ListNode first, ListNode second) { ListNode dummyHead =...
Copy List with Random Pointer This problem is a classic deep copy scenario, similar to graph cloning (e.g., LeetCode 133). Approach: Traverse the list once to copy the next pointers. During this traversal, store the mapping between original nodes and their copies in a hash map. Traverse the list a s...
Given an array of integers nums and an integer target, return the indices of two numbers that add up to the target value. Example: Input: nums = [3, 4, 2], target = 6 Output: [1, 2] Explanation: nums[1] + nums[2] equals 6 Approaches Brute Force Method: Iterate through each element and check every ot...
Working with singly linked lists requires a firm grasp of pointer manipulation and edge-case handling. The following sections break down three classic problems: removing nodes by value, building a custom linked list with index-based operations, and reversing a list in-place. Eliminating Nodes with a...
Problem Description Given an integer array nums, return true if any value appears at least twice in the array, and return false if all elements are distinct. Example 1: Input: nums = [1,2,3,1] Output: true Example 2: Input: nums = [1,2,3,4] Output: false Example 3: Input: nums = [1,1,1,3,3,4,3,2,4,2...
Minimum Time to Visit All Points Given integer coordinates points[i] = [xi, yi] for n points on a plane, calculate the minimum time in seconds to visit all points in the order given. Movement rules: Each second, move one unit horizontally, vertically, or diagonally (one unit in both directions). Exa...
Understanding the Problem The objective is to verify if a given integer is a palindrome. A palindrome reads the same backward as forward. For integers, this means that if we reverse the sequence of digits, the value remains identical. The problem imposes a strict constraint: the solution must not us...
Problem Statement Given a sorted integer array nums, remove duplicates in-place sothat each unique element appears no more than twice. Return the new length of the array. Key constraints: Must modify the input array in-place Space complexity must be O(1) The function receives the array by reference...
27. Remove Element Problem Link Remove Element Problem Description Given an array nums and a value val, remove all instances of that value in-place and return the new length. Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory....