The Two Pointers technique, as the name suggests, involves using two pointers to traverse an array or sequence. Sep 8, 2024 · The Two pointers' techniques are maintained to traverse the array or list. By applying this technique to find all pairs of integers that sum to a given target in an array of distinct integers, students will learn to optimize their solutions beyond naive approaches. Sep 13, 2025 · Understand the core principles behind two-pointer algorithms and apply them to real-world scenarios. Common patterns in the two-pointer approach involve: Oct 15, 2019 · Description Discussion This tutorial delve into the powerful Two Pointer Approach. 1st variant: Return YES if there exist two numbers such that their sum is equal to the target. Jul 12, 2025 · Two-Pointers approach: This problem follows the Two Pointers pattern and shares similarities with Triplet Sum to Zero. We will use the integers 0, 1, and 2 to represent the color red, white, and blue, respectively. Jul 8, 2025 · By using two pointers to traverse data structures (typically arrays or strings), we can solve complex problems with optimal time complexity, often transforming O (n²) solutions into O (n) The Two Pointer Technique The two pointer technique is a near necessity in any software developer's toolkit, especially when it comes to technical interviews. Iterating two monotonic pointers across an array to search for a pair of indices satisfying some condition in linear time. The two-pointer technique I’m referring to here involves using two pointers that start at opposite ends of an array and gradually move towards each other before meeting in the middle. Boost your coding skills and solve array problems efficiently with O (n) solutions. Essentially, it involves using two pointers (or indices) to traverse an array, often with each moving at a different speed or starting position. By leveraging two pointers to traverse the data structure, we can often reduce the time complexity and achieve more optimal solutions. But what are pointers? Jan 7, 2024 · The two pointers help to efficiently slide the window by updating the pointers. It helps solve problems that involve searching, sorting, or traversing arrays, strings, or linked lists in an efficient way. Step 3: Use Two Pointers to Find Pairs Nov 6, 2025 · Day 2: Reverse an array using two pointer approach This is a very commonly asked question. This approach works in constant space. LeetCode Problems solved in this video: Thanks for Watching! If you found this video helpful, check other Geekific By using this approach we are able to complete this problem efficiently, in O(n) time (we must iterate through the entire list once) and O(1) space complexity (we always use only three variables no matter what size the list is: two pointers and a counter). Sep 2, 2025 · Given a head of linked list where each node has two links: next pointer pointing to the next node and random pointer to any random node in the list. If you are preparing for Oct 3, 2023 · The two-pointer technique is one of those techniques. Aug 11, 2020 · Two-pointer technique is commonly used to solve array problems very efficiently. Approach 04: Two Pointer First, sort the array and then use the two-pointer left, right and iterate them over the array. Learn the Two Pointers Technique in Java DSA with introduction, when to use, advantages, examples, and popular problems. Inward traversal This approach has pointers starting at opposite ends of the data structure and moving inward toward each other: Feb 22, 2022 · Space complexity: O(n) The extra space required depends on the number of items stored in the table, which stores at most n elements. The contents of the memory location pointed by these two pointers are swapped and then the value of first pointer is increased and that of second pointer is decreased . It uses two pointers to traverse data in tandem, reducing unnecessary computations. Create a clone of this linked list. It involves using two pointers, one pointing to the beginning of the data set and the other pointing to the end, and moving them towards each other based on specific conditions. Now, that you are familiar with the basics of arrays from the last class, Manvi Two Pointers Technique Two pointers technique is a commonly used algorithmic approach to solve various problems that require linear time complexity. Oct 15, 2019 · Description Discussion This tutorial delve into the powerful Two Pointer Approach. Apr 11, 2025 · In the previous article, we discussed an array optimization technique called the Sliding Window Technique. Two pointers run through the data structure in the two-pointer pattern until one or both meet the required criteria. The Two Pointer Technique is a powerful algorithmic approach used to solve problems involving arrays, strings, or sequences by using two variables (pointers) to traverse the data structure. Binary search you can quickly find a peak in an array, two pointer search you can find maximum peak. Sep 15, 2025 · The Two-Pointers Technique is a simple yet powerful strategy where you use two indices (pointers) that traverse a data structure—such as an array, list, or string—either toward each other or in the same direction to solve problems more efficiently. Additionally, it is a simple approach that, when applied correctly, is extremely powerful. Jan 21, 2023 · One of these approaches goes by Two-Pointers and is the subject of this video. Oct 6, 2024 · For each fixed number, we will then use the two-pointer technique to find two other numbers such that the sum of the three numbers equals zero. Otherwise, return NO. Removing Duplicates: In a sorted array or list, you can use two pointers to remove duplicate elements in-place. . That’s it. These pointers can move towards each other, in the same direction, or even at different speeds. 2nd v Jul 10, 2024 · The two pointers technique is a versatile and efficient approach to solving a variety of problems involving arrays and strings. It's the use of two different pointers (usually to keep track of array or string indices) to solve a problem involving said indices with the benefit of saving time and space. 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. Time & space complexity: Apr 17, 2021 · Two are better than one if they act as one. Jul 10, 2024 · The two pointers technique is a versatile and efficient approach to solving a variety of problems involving arrays and strings. Some sample two pointer cases would be: search out from a center point, search in from edges, search one fast one slow to determine cycles/make index comparisons. Learn how it simplifies array and string problems with real-world examples and tips for coding interviews in 2025. This method is highly efficient when traversing arrays Mar 28, 2024 · What is the Two Pointers Technique? The Two Pointers technique involves using two pointers to navigate through a data structure like an array or a string. LeetCode Problems solved in this video: Thanks for Watching! If you found this video helpful, check other Geekific Jul 7, 2022 · One would resolve the two sum problem by using two pointers or a hash table algorithm If the input array is sorted or the output does not require returning array indices, one would use both two-pointers and hash table algorithm Master the two-pointer method with interactive visuals and real-time coding exercises to solve array problems efficiently. This technique is used to find a solution for problems that involve searching, sorting, or manipulating arrays, strings, or linked lists. Two pointer algorithm is one of the most commonly asked questions in any programming interview. In this article, we will look at another powerful approach: the Two Pointer Technique and Explore and run machine learning code with Kaggle Notebooks | Using data from No attached data sources Apr 17, 2021 · Two Pointers Approach — Python Code Two are better than one if they act as one. Example 1: Input: nums = [-4,-1,0,3,10] Output: [0,1,9,16,100] Explanation: After squaring, the array becomes [16,1,0,9,100]. Jan 13, 2022 · Hello, I have been solving all two pointers tagged problems in last 3. With the two pointer approach you aren't necessarily halving the search space. We then move the pointers based on the sum of the elements at these pointers. / Brute-force approach: time complexity: O (n3) / Two pointers: O (n2) / To apply two pointers: sort array, go through each element, The only difference between move zeroes and remove element's two pointers approach is their simple tweak in the if condition in the moveZeroes () method. This lesson guides you through an advanced array manipulation task using C#. At every step during the iteration, we will search for the quadruplets similar to Triplet Sum to Zero whose sum is equal to the given Sep 6, 2023 · Two Pointer Technique Two Pointer Technique is a useful strategy for solving a variety of array-based problems in a more efficient manner. Simple, right?! We use these multiple pointers to keep track of multiple indices of our input. pdf from ENCS COMP248 at Concordia University. We can follow a similar approach to iterate through the array, taking one number at a time. This is the best place to expand your knowledge and get prepared for your next interview. By understanding its applications and knowing when to use it, programmers can leverage the two-pointer approach to write elegant and efficient algorithms that tackle a wide range of array-related challenges. g. After sorting, it becomes [0,1,9,16,100]. This approach is best demonstrated through a walkthrough, as done below. This approach is generally used to search pairs in a sorted array. Example 2: Input Find the middle element of a linked list in Java using either the get () method or a single-pass two-pointer approach efficiently. Master the Two Pointers technique used in algorithmic problem-solving. As the name suggests, the two-pointer approach can be used to help process two elements per loop, instead of just one. Common patterns in the two-pointer approach involve: 4 days ago · View ArrayAlgo15. This approach optimizes the runtime by utilizing some order (not necessarily sorting) of the data. ⏱️ One minute! While preparing for coding interviews, one pattern I see again and again is the Two Pointer approach. The "two-pointer technique" only uses a small number of concepts, so don't worry. The name two pointers does justice in this case, as it is exactly as it sounds. The entire logic for reversing a string is based on using the opposite directional two-pointer approach! The Two Pointer Approach is one of the most used and efficient techniques to search for a pair in a sorted array. Problem: Minimum size subarray sum Oct 23, 2024 · The two-pointer technique is a fundamental and highly efficient approach for solving problems that involve searching, sorting, or manipulating arrays and strings. This approach helps in optimizing runtime to a great extent. util. Common patterns in the two-pointer approach involve: Sep 15, 2025 · The Two-Pointers Technique is a simple yet powerful strategy where you use two indices (pointers) that traverse a data structure—such as an array, list, or string—either toward each other or in the same direction to solve problems more efficiently. You may assume that each input would have exactly one solution, and you may not use the same element twice. By using pointers, we can process two elements per loop, instead of just one. Learn how this technique can be used to solve a variety of algorithmic problems, especially those involving arrays or linked lists. Given a sorted array A (sorted in ascending order), having N integers, find if there exists any pair of elements (A [i], A [j]) such that their sum is equal to X. Aug 6, 2024 · The concept of "two pointer technique" is not very extensive. See the below for the two pointers highlighted in yellow. We can iterate through the array one number at a time. The lesson covers sorting the array, pointer initialization, and pair identification Two pointers is a technique where we use two index variables to traverse a data structure, typically an array or string. Oct 3, 2023 · The two-pointer technique is one of those techniques. Sep 15, 2025 · The Two-Pointers Technique is a simple yet powerful strategy where you use two indices (pointers) that traverse a data structure—such as an array, list, or string—either toward each other or in the same direction to solve problems more efficiently Sep 15, 2025 · The Two-Pointers Technique is a simple yet powerful strategy where you use two indices (pointers) that traverse a data structure—such as an array, list, or string—either toward each other or in the same direction to solve problems more efficiently. We'll look into the working of it, implementation and use cases. Detailed solution for Two Sum : Check if a pair with given sum exists in Array - Problem Statement: Given an array of integers arr [] and an integer target. This is especially beneficial for sorted arrays. If you are preparing for Level up your coding skills and quickly land a job. In this technique pointers represent either index Visualize and solve the classic rainwater trapping problem with two-pointer approach and dynamic animations. The lesson includes detailed explanations, step-by-step code implementation, and complexity analysis to help you understand and effectively apply these techniques. Dec 1, 2025 · Unlock the power of the two pointer pattern! This comprehensive guide provides real-world examples, interview questions, and expert tips to ace your next coding challenge. This technique allows us to Jul 1, 2022 · Different approaches to tackle the Two Sum problem with explanation and time and space complexity Dec 21, 2019 · ^ arr[pointer] = arr[3] = 70 The two pointer approach involves the use of multiple pointers. The two pointer method is a helpful technique to always keep in mind when working with strings and arrays questions. The pointers move towards each other, away from each other, or in the same direction based on the problem's requirements. May 13, 2024 · Efficiency: The two-pointer approach often reduces time complexity by cleverly navigating the data structure without unnecessary iterations. This approach … Jul 23, 2020 · Intuition behind using a two pointers approach Asked 5 years, 5 months ago Modified 5 years, 5 months ago Viewed 247 times Nov 11, 2024 · 6- Many two-pointer problems ask for optimized time complexity, so if a brute-force solution feels too slow (O (n²)), two pointers might be a good fit for an O (n) approach. 5 months, and wanted to share my findings/classifications here. Instead of using a two-pointer or a binary search approach, we can utilize a HashTable to search for the required pair. Aug 21, 2025 · The two pointer technique is one of the most common and powerful patterns used in competitive programming, data structures, and algorithms. The key idea is that the pointers start at different positions and move in a coordinated way to traverse the data structure efficiently. The process of using a fast pointer and a slow pointer is another way to apply the two pointer technique, which can have O(n) time complexity and O(1) space complexity. There are two common scenarios in which the two-pointer approach is used. Learn now! Nov 16, 2024 · The Two Pointers technique is a highly efficient approach often used to solve problems that involve arrays or linked lists. Mar 17, 2025 · The two-pointer technique uses two-pointers or variables to iterate through a data structure, typically an array or linked list. You must solve this problem without using the library's sort function. Problem: Minimum size subarray sum This lesson introduces the two-pointer technique—a crucial algorithmic tool for efficiently solving array problems. Jul 26, 2023 · In this blog post, we will discuss a common problem: how to efficiently remove duplicates from a sorted array using the two-pointers approach and in-place modification. Apr 4, 2025 · In the two-pointer approach, pointers refer to an array’s indexes. e. For the purpose of this article, a pointer is an index of an array. Nov 18, 2022 · Aren't arrays amazing? They enable us to solve complex problems conveniently. In problems where we deal with… The Two Pointer Approach is one of the most used and efficient techniques to search for a pair in a sorted array. If you are preparing for Jul 23, 2025 · Two pointers is really an easy and effective technique which is typically used for searching pairs in a sorted array. The idea to solve this problem is simple, we use two pointers import java. These pointers can move towards each other, away from each other, or in the same direction, depending on the problem Apr 26, 2022 · Two pointer algorithm pattern is one of the most commonly asked questions in any programming interview. May 20, 2024 · This approach works by initializing two pointers, one at the beginning (left) and one at the end (right) of the array. Arrays; class Main { … Apr 4, 2024 · The two-pointer technique is a widely used approach to solving problems efficiently, particularly scenarios involving arrays or linked lists. Whenever an array question deals with finding two numbers in an array that satisfy a certain condition, either Apr 12, 2025 · The Two Pointer technique is one of the most intuitive yet powerful problem-solving strategies used in competitive programming and system design questions involving arrays, strings, and linked lists. Mar 30, 2022 · Two Pointers algorithm is one of the most commonly asked questions in any Coding/Technical Interview. In this guide, we'll cover the basics so that you know when and how to use this technique. It covers sorting an array of unique integers and implementing the two-pointer technique to find and replace elements based on specific criteria. Hey LinkedIn 👋 📌 DSA Practice Update Today, I solved 1 problem: 1️⃣ Valid Palindrome 🔹 Approach – Valid Palindrome Used a two-pointer technique: Converted the string to lowercase Jan 13, 2023 · Approach : In reverse function we take two pointers one pointing at the beginning of the array, other pointing at end of the array. Jul 23, 2025 · Whether it is searching, manipulation, optimization, or comparison, the two-pointer approach excels in various problem-solving scenarios. There are three main strategies for using two pointers. It will cover the theory behind the approach, provide step-by-step examples, and discuss its time and space complexity. LeetCode Problems solved in this video: Thanks for Watching! If you found this video helpful, check other Geekific Master the two-pointer method with interactive visuals and real-time coding exercises to solve array problems efficiently. What is it? Instead of using two loops and comparing every element with Can you solve this real interview question? Squares of a Sorted Array - Given an integer array nums sorted in non-decreasing order, return an array of the squares of each number sorted in non-decreasing order. Two-pointer Strategies Two-pointer algorithms usually take only O (n) O(n) time by eliminating the need for nested for-loops. It's a clever optimization that can help reduce time complexity with no added space complexity (a win-win!) by utilizing extra pointers to avoid repetitive operations. If we use two pointers for this type of problem, we are often only passing through the array once with the two pointers, which means that the time complexity is often O(n). We'll go over the key concepts in this blog, explaining when and how to use the two pointer technique.

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