Find duplicate in array

Many times we need to determine the presence of duplicate or repeated elements in a javascript array such as when applying a duplicate validation over a field on a page. There are many ways to check for elements of same value in a javascript array and this article will outline a few of those.

Method 1 : Using an object A javascript object consists of key-value pairs where keys are unique. 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.

find duplicate in array

With this concept, we can easily find out if an array contains duplicate values using below steps. Checking for the entry should be done before adding otherwise, it will mark the array duplicate for the very first element.

find duplicate in array

Javascript code for this approach is given below. Note that here we are adding a boolean true as the value of object entry, but you can add any other value. In that case, the comparison should also be done with the same value that was added.

find duplicate in array

A Set object can be created with array values by directly supplying the array to its constructor. If the array has duplicate values, then they will be removed by the Set. This means that the Set will only contain unique array elements.

Note that the original array will not be modified. If we compare the length of original array and the Set object created using this array and there is a mismatch, this clearly means that the array had at least one duplicate item. Javascript code for this method is given below. For calculating the size of array, use its length property and for getting the size of a Set object, use its size property. Set creating and comparison of its size with array length can also be performed in one-liner as.

Method 3 : Comparing the indexes of element This method works on comparing two indexes of array element, one is the first index and other is the last index.

At this point the loop should be terminated. Note that for getting the first index of an element use indexOf function with the element as argument and to get its last index, use lastIndexOf function.

Method 4 : Using some function Javascript some function checks all the elements of an array for a condition and returns true if any of the elements satisfy that condition.

LeetCode Find The Duplicate Number Explained - Java

The condition to be checked is supplied as an argument function to some. This function is a callback functionit is called for every array element one by one and should return either true or false. It is called till it returns falseonce it returns trueit is not called.

The argument function accepts three arguments. Logic In the argument callback function, we get the current array element as the first argument and the index of current element as the second argument. Now, we get the first index of the array element using indexOf function and compare it with the index supplied as the second argument.All elements of the array are in range 1 to n.

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And all elements occur once except two numbers which occur twice. Find the two repeating numbers. So the output should be 4 2. Method 1 Basic Use two loops. In the outer loop, pick elements one by one and count the number of occurrences of the picked element in the inner loop. Method 2 Use Count array Traverse the array once. While traversing, keep track of count of all elements in the array using a temp array count[] of size n, when you see an element whose count is already set, print it as duplicate.

Method 3 Make two equations Let the numbers which are being repeated are X and Y. We make two equations for X and Y and the simple task left is to solve the two equations. Similarly calculate product of input array, when this product is divided from n! Given sum and product of X and Y, we can find easily out X and Y. Using above two equations, we can find out X and Y.

Thanks to geek4u for suggesting this method. As pointed by Beginerthere can be addition and multiplication overflow problem with this approach. The approach used here is similar to method 2 of this post. Let the repeating numbers be X and Y, if we xor all the elements in the array and all integers from 1 to n, then the result is X xor Y.

Suppose that the kth bit of X xor Y is 1, we can xor all the elements in the array and all integers from 1 to n, whose kth bits are 1.

The result will be one of X and Y. Method 5 Use array elements as index Thanks to Manish K. Aasawat for suggesting this method. Note that this method modifies the original array and may not be a recommended method if we are not allowed to modify the array.

Writing code in comment? Please use ide. Python3 program to Find the two. This code is contributed by Smitha Dinesh Semwal.

Write "Repeated Elements are :". Python3 code for Find the two repeating. This code is contributed by Nikita Tiwari.Sign in to comment. Sign in to answer this question. Unable to complete the action because of changes made to the page. Reload the page to see its updated state.

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Find Duplicate in Array

You may receive emails, depending on your notification preferences. Finding Indices of Duplicate Values. RDG on 19 Nov Vote 2. Commented: Matt Fetterman on 2 Mar Accepted Answer: Simon. Suppose, I have a variable. How can I find the indices of duplicate values for column ?

I am using Matlab Ra. Thank you in advance. Accepted Answer. Simon on 19 Nov Vote 5. Cancel Copy to Clipboard. You may use "unique". The second output is the index of all unique values, e.Arrays a kind of data structure that can store a fixed-size sequential collection of elements of the same type.

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. Instead of declaring individual variables, such as number0, number1, …, and number99, you declare one array variable such as numbers and use numbers[0], numbers[1], and …, numbers[99] to represent individual variables.

A specific element in an array is accessed by an index. All arrays consist of contiguous memory locations.

The lowest address corresponds to the first element and the highest address to the last element. The program output is also shown in below. The Output of the program is shown above. If you found any error or any queries related to the above program or any questions or reviewsyou wanna to ask from us ,you may Contact Us through our contact Page or you can also comment below in the comment section.

We will try our best to reach up to you in short interval. Thanks for reading the post…. What is an Array? Enter array size Max : 50 :: 8. Enter array elements Enter arr [ 0 ] Element :: 1. Enter arr [ 1 ] Element :: 2. Enter arr [ 2 ] Element :: 3.

Enter arr [ 3 ] Element :: 4. Enter arr [ 4 ] Element :: 5. Enter arr [ 5 ] Element :: 2. Enter arr [ 6 ] Element :: 3. Enter arr [ 7 ] Element :: 6. Stored Data in Array Duplicate Values in Given Array are Process returned 0.

Like this: Like Loading Leave a Reply Cancel reply.In this program, we need to print the duplicate elements present in the array. This can be done through two loops.

The first loop will select an element and the second loop will iteration through the array by comparing the selected element with other elements. If a match is found, print the duplicate element. In the above array, the first duplicate will be found at the index 4 which is the duplicate of the element 2 present at index 1.

So, duplicate elements in the above array are 2, 3 and 8. JavaTpoint offers too many high quality services. Mail us on hr javatpoint. Please mail your requirement at hr javatpoint. Duration: 1 week to 2 week. Next Topic. Spring Boot. Selenium Py. Verbal A. Angular 7. Compiler D. Software E. Web Tech. Cyber Sec. Control S. Data Mining. Javatpoint Services JavaTpoint offers too many high quality services. Program to print the duplicate elements of an array.

Explanation In this program, we need to print the duplicate elements present in the array. Algorithm Declare and initialize an array. Duplicate elements can be found using two loops.

The outer loop will iterate through the array from 0 to length of the array. The outer loop will select an element. The inner loop will be used to compare the selected element with the rest of the elements of the array. If a match is found which means the duplicate element is found then, display the element.Toggle navigation Home. Write a program in Java to find duplicate elements in an integer array. Algorithm to find duplicate numbers in an integer array. Given an array of integers which may contains duplicate elementswe have to print all duplicate elements of array once.

To find duplicate elements, we will count the frequency of each elements of array and store it in a Map. If frequency of any element is id more than 1, then it is a duplicate element otherwise it is a unique element.

Algorithm to find duplicate elements in Array Declare an integer array "inputArray" for storing input array elements. Declare a Map to store the frequency of elements of inputArray. Using for-each loop, traverse input array and for each element check whether element exists in Map or not.

If present in map, increment it's count, other wise create a new entry in Map with count as 1. Labels: JavaJava Programs. Newer Post Older Post Home. Java Program to Concatenate Two Strings. Java Program to Find Length of a String.

Find duplicate elements in an array

All Java Programs.In this post, we will learn to find duplicate elements in array in java using Brute Force method, using Sorting method, using HashSetusing HashMap and using Java 8 Streams. In this method, we compare each element of an array with other elements. If any two elements are found equal, we declare them as duplicates.

In this method, We use HashMap to find duplicates in array in java. We store the elements of input array as keys of the HashMap and their occurrences as values of the HashMap.

Using this method, you can also find the number of occurrences of duplicates. The time and space complexity of this solution is O n. Duplicate Element : — found 2 times. How to remove duplicate elements from an array in java?

How to find common elements between two arrays in java? How to remove duplicate elements from an ArrayList in java? Can we achieve this in Integer??

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Please help. In above all programs we are not giving the input at runtime. This program does print the same duplicate element multiple times if its present more than twice. Your email address will not be published.

2 Ways to find duplicate elements in an Array - Java

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Skip to content. MainMenu MainMenu. Terry March 30, pm. What will be the time complexity for both the methods?

Sandeep January 3, am. Max April 28, am. Rahul October 8, pm. Mahendran October 9, am. Chandu September 19, pm. Bharath December 26, am. Chinta Divya Vani May 15, am. Pradeep kumar June 14, pm. Amarshi July 8, am. Nancy August 2, pm. Himanshu February 2, pm. Harsh kumar July 30, am. Sir,what is the need of i! Harsh It avoids element comparing with itself.

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