Find duplicate pairs in array. If the value is already in seen_values, skip it.

Find duplicate pairs in array. The simplest way to remove duplicates is by converting a list to a set. Better than official and forum solutions. duplicated() gives you a boolean series indicating which rows in a dataframe are duplicated like below: 0 False 1 False 2 False 3 False 4 True 5 False 6 True 7 True 8 True 9 True 10 True dtype: bool It however does not tell you which row the duplicates are duplicates of. Iterate over the array using a for loop. Pair of indexes (P,Q) such that 0 <= P < Q < N such that A[P] = A[Q]. Apr 27, 2023 · Create a new dictionary called result_dict to store the non-duplicate values. I'd be curious to see how they perform relative to each other. ---This video is based Jul 18, 2012 · As of numpy version 1. Loop through the key-value pairs in the original dictionary (test_dict). Jun 4, 2019 · To avoid duplicates, either add the result pairs (in a defined order) to a set or remove duplicates in the input itself. Find All possible Pairs in given Array Ask Question Asked 7 years, 6 months ago Modified 4 months ago Jul 23, 2025 · The idea is to use a hash set to store elements of one array and for each element in the second array, calculate the required complement that would sum to X and check if this complement exists in the hash set. The method should print the index pairs where sum of the values present in those indexes equal to the 2nd The question is ambiguous as to if the pair returned should be from unique array indexes. It’s a versatile and efficient method that appears in a wide range of scenarios, from finding pairs that meet specific criteria to removing duplicates. Mar 31, 2023 · Given a dictionary, the task is to find keys with duplicate values. Method 1. So the output should Learn how to efficiently find all unique pairs in an array with step-by-step solutions and code examples. May 14, 2024 · How can I find the indices of duplicate values for column 3:4? I am using Matlab R2013a. So, we sum up m (m - 1) / 2 for each unique x, giving us the answer. Find All Duplicates in an Array. You can then . For instance, if we have an array [1, 2, 3, 2, 5, 1], we aim to write a Python program that prints the duplicates, in this case [1, 2]. Jan 26, 2025 · The “Find All Duplicates in an Array” problem demonstrates an efficient use of in-place modifications and index mapping to detect duplicates. Print "YES" if there is any duplicate value in Tagged with cpp, array, duplicate, programming. . Jul 23, 2025 · [Better Approach] Sorting and Two Pointer technique - O (n*log n) Time and O (1) Space The idea is to sort the array and use two pointers at the beginning and end of the array. Mar 6, 2021 · Given an array of positive integers, find all the duplicates. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type. Discover tips, tricks, and code examples for quick implementation. 1st is an integer array and 2nd is an integer. We will look into problem statement, sample data, and Python Nov 23, 2024 · Discovering Methods to Identify Duplicate Values in JavaScript Arrays The task of checking whether an array contains a duplicate value can often arise in JavaScript programming. Find the solution of Find All Duplicates in an Array Leetcode question with step by step explanation in 4 approaches and 3 solutions in languages like Java, CPP, Python. Then, iterate through the hashmap and add any element with a frequency greater than 1 to the result. With extra space it means extra space of order O(n). He iterates over the array and for each value either increments the value or creates the key value pair (the value of the non-existent key evaluates to undefined so the || or operator takes a Mar 24, 2020 · Learn 5 different ways to check if an array contains duplicate elements with example and explanation. Apr 29, 2024 · During interviews, this concept may be presented as ‘ Write an algorithm to detect duplicates in an array ’ or ‘ Find duplicate pairs in an array ‘. Jan 29, 2021 · I want to find duplicate elements in a dynamic array. Method Apr 21, 2017 · Given one array A=[ 1 1 2 3 5 6 7]. I have gotten this to Jul 11, 2025 · Given an array of N elements, the task is to find all the unique pairs that can be formed using the elements of a given array. We observe that if there are m occurrences of the number x in A, then the number of ascending duplicate pairs of the value x is m choose 2, or m (m - 1) / 2. One of the most common ways to find duplicates is by using the brute force method, which compares each element of the array to Oct 11, 2021 · In this article, we will discuss how to find duplicate values and their indices within an array in MATLAB. Below is the discussion of this program by two approaches: Jul 23, 2025 · Given an array arr [] containing 2*n + 2 positive numbers, out of which 2*n numbers exist in pairs whereas the other two number occur exactly once and are distinct. Here we will learn how to Remove Duplicate Elements from a 1-D NumPy Array and 2-D In-depth solution and explanation for LeetCode 442. For example, if two o Problem Description Given an integer array nums of length n where all the integers are in the range [1, n] and each element appears either once or twice, return an array of all the integers that appear exactly twice. If array = {2,4,6,4,6} and S = 8 then answer is { (2,6), (4,4)}. Approach: The basic idea is based on the hash map to solve the problem. Jul 11, 2025 · Given an array arr [] containing n integers where each integer is between 1 and (n-1) (inclusive). In this article, we explored three methods for finding duplicates in arrays: using hash tables, sorting, and using built-in functions. The task is to find the other two numbers. In this video, we'll are going to solve some more questions of the array. I'm finding duplicate elements in a given array. Find the two repeating numbers. numpy. Returns the sorted unique elements of an array. Problem Statement Imagine you are tasked with verifying the Find All Duplicates in an Array - Leetcode 442 - Python NeetCodeIO 269K subscribers Subscribe Python: Average specific elements in a third array by the indexes of duplicate pairs of long and lat in two other arrays，程序员大本营，技术文章内容聚合第一站。 Feb 7, 2013 · Depending on meaning of "unique pair" array {1, 1, 1, 1} may contain 1, 2 or 6 "unique pairs". Then, a single pass is made to compare each element with its previous one. Mar 15, 2024 · I have an array of value,location pairs arr=(test,meta my,amazon test,amazon this,meta test,google my,google hello,microsoft) I want to print the duplicate values, the number/count of them, along LINQ: Find Duplicates (advanced example with objects) | Test your C# code online with . Counting the Same Elements Twice: Mistake: Counting the same element twice when considering pairs. How can we detect this duplicate in time O (n)? For example, an array of 4,1,2,3 would become 4,1,2,2. Jul 19, 2024 · Finding duplicates in an array of objects is a common task in JavaScript, especially when dealing with data manipulation and validation. Apr 22, 2025 · Finding duplicates in arrays is a common problem in programming, and there are several ways to solve it. The idea is to insert each array element `arr[i]` into a set. Using set () We can use set () to remove duplicates from the list. Find All Duplicates in an Array (Solution Explained) Nick White 402K subscribers 3. Given an array that may contain duplicates, print all repeated/duplicate elements and their frequencies. Initialize two pointers at the beginning and end of the array. Nov 24, 2021 · I want to know if there is a any way to find out how many pairs is in a sorted array The easiest way is using two for loop for (int i = 0; i &lt; arr. unique has an argument return_counts which greatly simplifies your task: u, c = np. If such pair is present, we print the pairs. Let’s see the naive solution. Jul 11, 2025 · In this article, we'll learn several ways to remove duplicates from a list in Python. All elements of the array are in the range of 1 to N. Apr 30, 2024 · The question ' Find duplicate elements in an array ' is frequently posed in interviews. Mar 7, 2025 · Finding pairs in an array that sum up to a target is a common problem with different trade-offs. length; i++) { for (int j = i + 1; j & Jul 26, 2020 · Given an array A with zero index and N integers find equal elements with different positions in the array. The first two solutions presented will output a solution when the duplicate of a single value in the array is the sum. Jul 9, 2016 · @web_dev he creates an associative array object called count that will have a key value pair for each unique element in the array, where the key is the unique element value and the value is the count. Please refer to Duplicates in an array in O (n) and by using O (n) extra space for implementation of naive approach. If you try to add a duplicate key with a different value, then the older value for that key is overwritten by the new value. Jul 22, 2025 · The main idea is to first sort the array so that duplicate elements appear next to each other. However, this approach does not preserve the original order. This approach avoids additional space usage Oct 27, 2022 · Determine duplicates/pairs in an array in C++ Asked 3 years ago Modified 3 years ago Viewed 517 times Sep 26, 2025 · Learn how to identify duplicate pairs in an array, understand different approaches including a naive and an optimized method in Python. You must solve the problem without modifying the array nums and using only constant extra space. Nov 2, 2014 · 2 From your code, it looks like the goal is to return the count of ascending duplicate pairs in A. During interviews, this concept may be presented as 'Write an algorithm to detect duplicates in an array' or 'Find duplicate pairs in an array'. For each key-value pair, check if the value is already in seen_values. Is there a clever way of identifying which rows May 30, 2013 · Is there a way to find duplicate pairs in multiple columns in Excel? For instance, column1 column2 Smith Jones &lt;-- duplicate pair Smith Johnson Jones Jul 1, 2025 · There are multiple ways to find duplicate elements in an array in Java and we will see three of them in this program. Oct 24, 2024 · Given an array with distinct elements, the task is to find the pairs in the array such that a % b = k, where k is a given integer. flatMap () the frequencies to an array containing your number for each pair you found like so: Apr 30, 2024 · In this blog post, I'll be elucidating how to identify similar items within an array. You can grab the frequency of each number, and then filter out any which have an odd frequency. Given an integer array nums of length n where all the integers of nums are in the range [1, n] and each integer appears at most twice, return an array of all the integers that appears twice. Jan 15, 2024 · Problem 1 You will be given an array arr of size n. We can return pairs in any order, but all the returned pairs should be internally sorted, that is for any pair(i, j), i should be less than j. Jul 31, 2023 · Can you solve this real interview question? Find All Duplicates in an Array - Given an integer array nums of length n… Sep 1, 2025 · The idea is to sort the array and use two pointers technique to find all the pairs. In-depth solution and explanation for LeetCode 2815. I know a solution to print all the pairs in the array but how do we print unique pairs? Aug 6, 2025 · The very basic approach is to generate all the possible pairs and check if any pair exists whose sum is equals to given target value, then increment the count variable. Example 1: Input: nums = [1,3,4,2,2] Output Aug 11, 2016 · Just use an array sort in O (n) time instead of one in O (nlg (n) time, this of course assuming you can use something like radix or counting sort on your input (which with your given integer ranges, you could). Mar 14, 2022 · Learn how to write a JavaScript program to efficiently find duplicate elements in an array. Mar 4, 2025 · Given an array arr [] of N+2 elements. Jul 3, 2025 · Today, we are going to look at another interesting programming question from the array; write a program to find all pairs of integers whose sum is equal to a given number. Using JavaScript filter () Method with indexOf method The array. Let's discuss a few methods for the same. Dec 30, 2012 · I am looking to write a simple and easy method that will allow me to find a pair of duplicates in an array and display the index number of which the pair would exist. My example could be easily modified to implement either variant, I just chose meaning that was simpler to implement. If the value is already in seen_values, skip it. Stay with us to verify 'whether an array contains duplicates'. During interviews, this concept may be presented as 'Write an algorithm to detect duplicates in an array' or 'Find duplicate pairs in Jul 23, 2025 · Finding duplicates in a list is a common task in programming. And all elements occur once except two numbers which occur twice. This will guide you through the process of identifying duplicate objects in an array using various techniques. For example, if the input integer array is {2, 6, 3, 9, 11} and the given sum is 9, the output should be {6,3}. You have an array of numbers from 0 to n-1, one of the numbers is removed, and replaced with a number already in the array which makes a duplicate of that number. For example if sum=10 and array=[5,1,2,3]. In this blog post, I'll be elucidating how to identify similar items within an array. It will include only those elements for which true is returned. There is only one duplicate element, find the duplicate element in O (n) time complexity and O (1) space. If the value is not in seen_values, add the key-value pair to result_dict. 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. The solution and logic shown in this article are generic and apply to an array of any type e. How can I solve that part. Find All Duplicates in an Array in Python, Java, C++ and more. Can you solve this real interview question? Find All Duplicates in an Array - Given an integer array nums of length n where all the integers of nums are in the range [1, n] and each integer appears at most twice, return an array of all the integers that appears twice. Code Implementation: Third, find if there's any duplicates in the array: if 'x' is duplicated, then 'x' and 'S-x' must have occurred in the original array, and you've found your pair. Is it possible to solve it without any extra space and O(n) time? Mar 30, 2016 · You find 3 because you don't check if current number is already count as duplicate : the first 4, you find a duplicate, and the second one also. May 31, 2024 · Handling Duplicate Pairs: Ignoring duplicate pairs: Mistake: Overlooking the possibility of duplicate pairs in the array. If no duplicates are found add -1 to the result. For any arbitrary maximum in the list to be checked for duplicates, radix sort grows exactly the same as other efficient sorts, specifically it must sort at most n elements in up to log (n) passes, so radix is O (n log (n)). Now, compare the sum of elements at these pointers: If sum = target, store the pair and skip duplicates to ensure they are distinct. Jan 6, 2024 · Let’s compare the provided solution (which uses array negation) with a solution that uses a map (or dictionary) to find duplicates in an array. If `k` is more than the array's size, the solution should check for duplicates in the complete array. Input: arr [] = {1, 2, 3} Output: 9 Naive approach: The simple solution is to iterate through every possible pair and add them to a set and then find out the size Jul 12, 2025 · Approach: In order to find all the possible pairs from the array, we need to traverse the array and select the first element of the pair. Explore efficient algorithms examples to identify the unique element in an array where every other number appears twice. We use nested loops to traverse through all possible pairs of elements Sep 9, 2025 · Given an array and a positive number `k`, check whether the array contains any duplicate elements within the range `k`. You have to check if the current number isn't in the begin of array. g. Declare an empty object. Examples: Input: arr [] = {1, 1, 2} Output: 4 (1, 1), (1, 2), (2, 1), (2, 2) are the only possible pairs. Then we need to pair this element with all the elements in the array from index 0 to N-1. May 8, 2018 · 1 Find all unique pairs of the element in an array that sum to S. Jul 23, 2025 · Two pointers is really an easy and effective technique which is typically used for searching pairs in a sorted array. Dec 13, 2019 · I have a method which accepts two parameters. Method #1: Using Naive approach In this method first, we convert dictionary values to keys with the inverse mapping and then find the duplicate keys In this particular case, the distribution of keys is such that no two are equal, except that there is one duplicate pair. Aug 10, 2020 · Here are few methods to check the duplicate value in javascript array. Nov 27, 2020 · The frequency of an element in an array is the count of the occurrence of that particular element in the whole array. In Python, there are several ways to do this. The solution will output (5,5). Mar 9, 2023 · I am trying to find all the objects that contain the same key value pair and create a new array of objects with the duplicate objects with the number of times they were found. Stay with us to verify ' whether an array contains duplicates '. NET Fiddle code editor. If sum < target, we move the left pointer towards right. Approach: This solution leverages the fact that the array elements are within the range from 1 to n, where n is the size of the array. In most cases it works, but how can it work for this case. Aug 31, 2013 · Now just a wonder, let's say that duplicated int are distributed into n int arrays, im using dictionary and for loop to understand which array contains a duplicate and remove it according to a logic of distribution, is there a fastest way (linq wondering) to achieve that result ? thank you in advance for interest. The hash set method is best for speed, while the two-pointer method is best for reducing memory usage. filter () method creates a new array of elements that matches the passed condition through the callback function. Intuitions, example walk through, and complexity analysis. 9. The solution must run in O (n) time and use only constant extra space (excluding the output array). String array or integer array or array of any object. Jul 23, 2025 · The duplicate elements are removed as shown below: 2. Examples: Input: arr = [4, 2, 4, 5, 2, 3, 1], N = 5 Output: 4 2 Explanation: The above array has n + 2 = 7 elements with all elements occurring once except 2 and 4 which occur twice. unique(a, return_counts=True) dup = u[c > 1] This is similar to using Counter, except you get a pair of arrays instead of a mapping. This article explores various methods to achieve this in Python, incorporating different programming paradigms and Pythonic ways. Welcome back, readers. 8K Jul 14, 2024 · Learn how to find the single number in an array in Python. Solution: Account for duplicate pairs and decide whether to include them in the result or not. Forex. But, the numbers in the array are from 0 to n-1, and the input array has length n. If the sum of the elements at these pointers equals target, we update the pair counter and skip duplicates to ensure they are distinct. Feb 2, 2024 · In this article, we'll go through the steps necessary to find the duplicate elements in a list using various methods in C#. But there is one problem that my duplicate elements can repeat too. Max Pair Sum in an Array in Python, Java, C++ and more. Dec 27, 2016 · What is an Array ? Arrays a kind of data structure that can store a fixed-size sequential collection of elements of the same type. Mar 26, 2015 · The function pd. It can be done using unique (), length (), setdiff (), and numel () functions that are illustrated below: Using Unique () Unique (A) function is used to return the same data as in the specified array A without any repetitions. Identifying duplicate elements in an array is a common programming task, and it often involves searching through the array to find and handle these repeated values appropriately. If a pair of adjacent elements is equal, the function returns true, indicating the presence of duplicates. Sep 6, 2021 · How to Find Duplicates in Nested Arrays of Objects A flexible algorithm that works for any depth of nesting Parsing through data is one of life’s great joys/headaches. 0, np. D Apr 29, 2024 · The question 'Find duplicates elements in an array' is frequently posed in interviews. Syntax This tutorial explains how to find all pairs in an array that add up to a given target sum. There are three optional outputs in addition to the unique elements: the indices of the input array that give the unique values the indices of the unique array Given an array of n integer elements how will you find whether there are duplicates in the array in O(n) time without using any extra space. Arrays are really important because we are going to use them a lot in future topics Jun 28, 2023 · This approach follows a brute force method of comparing each number with every other number in the array to find duplicates. Iterate through the array, updating the frequency count for each element in the hashmap. There is only one repeated number in nums, return this repeated number. Learn how to efficiently identify and count duplicates in a two-dimensional array with this step-by-step guide and code examples. Examples : Input : arr [] = {1, 4, 3, 4, 2} Output : 4Input : arr [] = {1, 3, 2, 1}Output : 1 Jul 23, 2025 · Output: 3 Explanation: The number 3 appears more than once in the array. Below is the step by step approach: Traverse the array and select an element in each traversal. If no duplicates are found after traversing the entire array, the function returns false. You may assume that a and b are in small range Oct 11, 2024 · Given an array arr [] and a target value, the task is to find all possible indices (i, j) of pairs (arr [i], arr [j]) whose sum is equal to target and i != j. Jul 23, 2025 · To find duplicates in an array, start by creating an empty hashmap to track the frequency of each element. Index 4 for example could be a duplicate of 0,1,2,3 or 5. unique # numpy. Thank you in advance. I need help to known the indices where there are duplicate values. Jan 8, 2024 · A quick look at several algorithms for finding pairs of numbers in an array that add up to a given sum in Java using traditional for loops and the Java 8 Stream API. Mar 14, 2025 · Given an array where every element appears exactly twice except for one element that appears once , and all duplicates are adjacent. Mar 7, 2024 · Problem Formulation: Identifying duplicate elements in an array is a common task that can be required in various contexts. I wrote this code in C++ as part of a uni task where I need to ensure that there are no duplicates within an array: // Check for duplicate numbers in user inputted data int i; // Need to decla Oct 20, 2021 · I am currently practicing for coding interviews and am working on a function that takes in an array and the size of that array and prints out which numbers in it are duplicates. It's probably worth mentioning that even though np. unique is quite fast in practice due Jul 23, 2025 · The main idea is to first sort the array arr[] and then iterate through it to check if any adjacent elements are equal. Below, we present a collection of methods to determine if a specific value exists within an array effectively, while discussing potential pitfalls as well. Using a Set (Most Efficient for Large Lists) Set () method is used to set a track seen elements and helps to identify duplicates. Example of array declaration in Java: Sep 12, 2025 · Given an unsorted integer array, print all pairs with a given difference `k` in it. Example 1: Input: nums = [1,3,4,2,2] Output Jul 23, 2025 · In this article, we will see how to remove duplicate elements from NumPy Array. Can you solve this real interview question? Find the Duplicate Number - Given an array of integers nums containing n + 1 integers where each integer is in the range [1, n] inclusive. In every iteration, add a new entry Sep 3, 2022 · This tutorial explains how to remove duplicate elements from a NumPy array, including several examples. Thanks Can you solve this real interview question? K-diff Pairs in an Array - Given an array of integers nums and an integer k, return the number of unique k-diff pairs in the array. unique(ar, return_index=False, return_inverse=False, return_counts=False, axis=None, *, equal_nan=True, sorted=True) [source] # Find the unique elements of an array. Using an object A javascript object consists of key-value pairs where keys are unique. LeetCode 442. Let’s explore the efficient methods to find duplicates. Jan 2, 2010 · When working with sorted arrays, the two pointers technique is a game-changing approach that simplifies complex problems. Jul 4, 2025 · In other words, if there are two or more occurrences of the same value in an array, those values are considered duplicates. wyso 0j 5ozm ezymb mhoo cly8z4nr ucj atqdo3 o1vr ns