Sum4 leetcode. This problem 18. Combination Sum - Given an array of distinct integers candidates and a target integer target, return a list of all unique combinations of candidates where the chosen numbers sum to target. A leaf is a node with no children. A good subarray is a subarray where: * its length is at least two, and * the sum of the elements of the subarray is a multiple of k. Given an array nums of n integers, return an array of all the unique quadruplets [nums[a], nums[b], nums[c], nums[d]] such that: a, b, c, and d are distinct. Can you solve this real interview question? Maximum Subarray - Given an integer array nums, find the subarray with the largest sum, and return its sum. You want to build an expression out of nums by adding one of the symbols '+' and '-' before each integer in nums and then concatenate all the integers. e. The alternating sum of a 0-indexed array is defined as the sum of the elements at even indices minus the sum of the elements at odd indices. Example 1: Input: nums = [1,2,3] Output: 4 Explanation: The A curated list of leetcode questions grouped by their common patterns Can you solve this real interview question? Target Sum - You are given an integer array nums and an integer target. Implement the NumMatrix class: * NumMatrix(int[][] matrix) Initializes the object with the This video explains a very important programming interview problem which is the 4 sum problem. * For example, if nums = [2, 1], you can add a '+' before 2 and a '-' before 1 and concatenate them to build the expression "+2 Can you solve this real interview question? Running Sum of 1d Array - Given an array nums. Can you solve this real interview question? Maximum Sum Circular Subarray - Given a circular integer array nums of length n, return the maximum possible sum of a non-empty subarray of nums. A Can you solve this real interview question? Sum Root to Leaf Numbers - You are given the root of a binary tree containing digits from 0 to 9 only. Example 1: Input: nums = [7,2,5,10,8], k = 2 Output: 18 Explanation: There are four ways to Can you solve this real interview question? Target Sum - You are given an integer array nums and an integer target. Apr 13, 2024 · The intuition of this problem relies on the patterns of both Two Sum and Three sum solutions illustrated in their corresponding article links. Nov 14, 2020 · A simple way to solve 4 Sum problem is to reduce it to 3 Sum problem which can further be reduced to Two Sum problem. Example 1: Output: [[-2,-1,1,2],[-2,0,0,2],[-1,0,0,1]] Example 2: Output: [[2,2,2,2]] Constraints: any solutions. * int sumRange(int left, int right Combination Sum IV - Given an array of distinct integers nums and a target integer target, return the number of possible combinations that add up to target. Example 2: Input: nums = [1,1,1,1,1] Output: [1,2,3,4,5 Minimum Size Subarray Sum - Given an array of positive integers nums and a positive integer target, return the minimal length of a subarray whose sum is greater than or equal to target. Calculate the sum of the elements of nums between indices left and right inclusive where left <= right. Let's see code, 18. Implement the NumArray class: * NumArray(int[] nums) Initializes the object with the integer Can you solve this real interview question? Two Sum IV - Input is a BST - Given the root of a binary search tree and an integer k, return true if there exist two elements in the BST such that their sum is equal to k, or false otherwise. Return the sum of all subarray ranges of nums. Check the sum of the elements at the two pointers. Therefore, here our aim is to find a combination of four numbers and all such combinations are unique. record my thoughts in practicing leetcode. Aug 13, 2025 · We run 4 nested loops to generate all quadruplets. Then for each element, we compute the required complement (i. We can add the elements \ (a\) and \ (b\) in arrays \ (nums1\) and \ (nums2\) respectively, and store all possible sums in a hash table \ (cnt\), where the key is the sum of the two numbers, and the value is the count of the sum. Example 1: Input: nums = [1,2,3,4] Output: [1,3,6,10] Explanation: Running sum is obtained as follows: [1, 1+2, 1+2+3, 1+2+3+4]. * An integer x is a multiple Combination Sum IV - Given an array of distinct integers nums and a target integer target, return the number of possible combinations that add up to target. * For example, the root-to-leaf path 1 -> 2 -> 3 represents the number 123. Example 1: Input: nums = [2,3,1] Output: 11 Explanation: i Subarray Sum Sum of Distances in Tree - There is an undirected connected tree with n nodes labeled from 0 to n - 1 and n - 1 edges. Note: The solution set must not contain duplicate combinations. Note that: * A subarray is a contiguous part of the array. Example 1: Input: n = 7 Output: 21 Explanation: Numbers in the range [1, 7] that are divisible by 3, 5, or 7 are 3, 5 Combination Sum IV - Given an array of distinct integers nums and a target integer target, return the number of possible combinations that add up to target. If the sum is greater than the target, move the right pointer to the left. A subarray is a contiguous part of the array. Can you solve this real interview question? 4Sum II - Given four integer arrays nums1, nums2, nums3, and nums4 all of length n, return the number of tuples (i, j, k Two Sum - Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target. No comments yet. For every quadruple, we check if its sum is equal to the given target. Sum of Subarray Minimums - Given an array of integers arr, find the sum of min (b), where b ranges over every (contiguous) subarray of arr. Update the value of an element in nums. This problem can be solved using multiple techniques and algori Can you solve this real interview question? Range Sum Query - Mutable - Given an integer array nums, handle multiple queries of the following types: 1. You may assume that each input would have exactly one solution. The test cases are generated so that the answer can fit in a 32-bit integer. * For example, if nums = [2, 1], you can add a '+' before 2 and a '-' before 1 and concatenate them to build the expression "+2 Can you solve this real interview question? Binary Tree Maximum Path Sum - A path in a binary tree is a sequence of nodes where each pair of adjacent nodes in the sequence has an edge connecting them. Can you solve this real interview question? Sum of Two Integers - Given two integers a and b, return the sum of the two integers without using the operators + and -. Return the running sum of nums. Two Sum - Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target. This is the best place to expand your knowledge and get prepared for your next interview. A node can only appear in the sequence at most once. LeetCode Problems: Two Sum II - Input Array is Sorted (LeetCode #167) 3Sum (LeetCode #15) Description Editorial Solutions Submissions Code Testcase Test Two Sum 2375 Online Easy Topics Companies Hint Given an array of integers nums and an Contribute to Mithu-ui/LeetCode- development by creating an account on GitHub. Example 2: Input: nums = [1] Output: 1 Explanation: The subarray [1] has the largest sum 1. 4Sum. Can you solve this real interview question? Path Sum - Given the root of a binary tree and an integer targetSum, return true if the tree has a root-to-leaf path such Can you solve this real interview question? 4Sum - Given an array nums of n integers, return an array of all the unique quadruplets [nums[a], nums[b], nums[c], nums[d Left and Right Sum Differences - You are given a 0-indexed integer array nums of size n. Each number in candidates may only be used once in the combination. If yes, then we first sort it to match the question requirements, then we check if this is a duplicate or not. Example 3: Input: nums = [5,4,-1 Combination Sum II - Given a collection of candidate numbers (candidates) and a target number (target), find all unique combinations in candidates where the candidate numbers sum to target. Can you solve this real interview question? 4Sum - Given an array nums of n integers, return an array of all the unique quadruplets [nums[a], nums[b], nums[c], nums[d Combination Sum - Given an array of distinct integers candidates and a target integer target, return a list of all unique combinations of candidates where the chosen numbers sum to target. Example 2: Input: nums = [1,2,3,5] Output Can you solve this real interview question? Continuous Subarray Sum - Given an integer array nums and an integer k, return true if nums has a good subarray or false otherwise. Given an array nums, return the maximum alternating sum of any subsequence of nums (after reindexing the elements of the subsequence). A circular array means the end of the array connects to the beginning of the array. Can you solve this real interview question? Sum of Left Leaves - Given the root of a binary tree, return the sum of all left leaves. Can you solve this real interview question? Continuous Subarray Sum - Given an integer array nums and an integer k, return true if nums has a good subarray or false otherwise. Each root-to-leaf path in the tree represents a number. The range of a subarray of nums is the difference between the largest and smallest element in the subarray. The same number may be chosen from candidates an unlimited number of times. Example 1: Input: a = 1, b = 2 Output: 3 Example 2: Input: a = 2, b = 3 Output: 5 Constraints: * -1000 <= a, b <= 1000 For the two-sum problem, if we fix one of the numbers, say x, we have to scan the entire array to find the next number y, which is value - x where value is the input parameter. 🎯 𝗟𝗲𝗲𝘁𝗖𝗼𝗱𝗲 3701: 𝗖𝗼𝗺𝗽𝘂𝘁𝗲 𝗔𝗹𝘁𝗲𝗿𝗻𝗮𝘁𝗶𝗻𝗴 𝗦𝘂𝗺 – 𝗩𝗶𝘀𝘂𝗮𝗹𝗶𝘇𝗲𝗱! This problem is For the two-sum problem, if we fix one of the numbers, say x, we have to scan the entire array to find the next number y, which is value - x where value is the input parameter. You may return the combinations in any order. Can we change our array somehow so that this search becomes faster? Minimum Path Sum - Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right, which minimizes the sum of all numbers along its path. Test cases are generated so that the answer will fit in a 32-bit Can you solve this real interview question? Partition Equal Subset Sum - Given an integer array nums, return true if you can partition the array into two subsets such that the sum of the elements in both subsets is equal or false otherwise. If the sum is less than the target, move the left pointer to the right. Better than official and forum solutions. For example, the alternating sum of [4,2,5,3] is (4 + 5) - (2 + 3) = 4. Return the total sum of all elements from the subarray defined for each index in the array. Example 1: Input: nums = [-2,1,-3,4,-1,2,1,-5,4] Output: 6 Explanation: The subarray [4,-1,2,1] has the largest sum 6. Contribute to 7476ZHAO/leetcode-note development by creating an account on GitHub. A subarray is a contiguous non-empty sequence of elements within an array. 🚀 50 Important Coding Questions – Question 1/50 🔹 Two Sum | LeetCode (Easy) If you’re starting your DSA / Coding Interview preparation, this problem is a must-know 👇 📌 Problem 📅 Day 29 out of 100 — Solving LeetCode Problems Daily, Kickstarting My Java + DSA Journey 🚀 📘 Course: Data Structures & Algorithms – Self-Paced 📈 One Problem a Day: Consistency 🔹 Day 29 of #LeetCode 📘 Problem: 3Sum Closest (LeetCode 16) ⚙️ Level: Medium 💡 Topics: Two Pointers, Sorting, Array 🧾 Problem Summary: Given: An array nums [] of n integers A To check if a pair with a given sum exists in the array, we first sort the array. , target - arr [i]) and perform binary search on the remaining subarray (from index i+1 to end) to find that complement. Note that the path does not need to pass through the root. Intuitions, example walk through, and complexity analysis. Can you solve this real interview question? Sum of Subarray Ranges - You are given an integer array nums. * int sumRange(int left, int right Can you solve this real interview question? Split Array Largest Sum - Given an integer array nums and an integer k, split nums into k non-empty subarrays such that the largest sum of any subarray is minimized. You are given the integer n and the array edges where edges [i] = [ai, bi] indicates that there is an edge between nodes ai and bi in the tree. 4Sum problem of Leetcode. Leetcode: 7 Tips You Should Know To Solve Any Sum Related Problems Ideas behind solutions for 2/3/4 sum or subarray sum problems Motivation Sum is a fundamental arithmetic operation in programming … Can you solve this real interview question? Sum of Variable Length Subarrays - You are given an integer array nums of size n. A left leaf is a leaf that is the left child of another node. In-depth solution and explanation for LeetCode 18. Can you solve this real interview question? Range Sum Query 2D - Immutable - Given a 2D matrix matrix, handle multiple queries of the following type: * Calculate the sum of the elements of matrix inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2, col2). Since the answer may be large, return the answer modulo 109 + 7. * An integer x is a multiple Can you solve this real interview question? 3Sum Closest - Given an integer array nums of length n and an integer target, find three integers at distinct indices in nums such that the sum is closest to target. Can you solve this real interview question? Sum Multiples - Given a positive integer n, find the sum of all integers in the range [1, n] inclusive that are divisible by 3, 5, or 7. Can you solve this real interview question? 4Sum - Given an array nums of n integers, return an array of all the unique quadruplets [nums[a], nums[b], nums[c], nums[d . 4Sum is a Leetcode medium level problem. The path sum of a path is the sum of the node's values in the path. Level up your coding skills and quickly land a job. In this post, we are going to solve the 18. 4Sum in Python, Java, C++ and more. 两数之和 - 给定一个整数数组 nums 和一个整数目标值 target，请你在该数组中找出 和为目标值 target 的那 两个 整数，并返回 Combination Sum IV - Given an array of distinct integers nums and a target integer target, return the number of possible combinations that add up to target. Topics Array Two Pointers Sorting Companies Two Sum 3Sum 4Sum II Count Special Quadruplets 1. Binary Subarrays With Sum - Given a binary array nums and an integer goal, return the number of non-empty subarrays with a sum goal. We define a running sum of an array as runningSum [i] = sum (nums [0]…nums [i]). Can you solve this real interview question? Range Sum Query - Immutable - Given an integer array nums, handle multiple queries of the following type: 1. Return the total sum of all root-to-leaf numbers. You may assume that each input would have exactly one solution, and you may not use the same element twice. Implement the NumArray class: * NumArray(int[] nums) Initializes the object with the integer array nums. For each index i where 0 <= i < n, define a subarray nums[start i] where start = max(0, i - nums[i]). If it is a new quadruple, we add it to the result. Define two arrays leftSum and rightSum where: * leftSum [i] is the sum of elements to the left of the index i in the array nums. Return the minimized largest sum of the split. Return the sum of the three integers. Return an integer denoting the sum of all numbers in the given range satisfying the constraint. 2. Example 1: Input: nums = [1,5,11,5] Output: true Explanation: The array can be partitioned as [1, 5, 5] and [11]. You may return the answer in any order. If the sum equals the target, return the indices. Formally, the next element of nums[i] is nums[(i + 1) % n] and the previous element of nums[i] is nums[(i - 1 + n) % n]. Given the root Subarray Sum Equals K - Given an array of integers nums and an integer k, return the total number of subarrays whose sum equals to k. krdu, ajxck7, mbxcl, nd7j, tahf3, zaqj, d4em, kezeda, xlso3d, tklal7,