moving all duplicate elements in an array into a separate array

Question

moving all duplicate elements in an array into a separate array

I am struggling to achieve the result [1,1,1,1,2,2,20,20] from the given array.

My goal is to extract all duplicate values into a new array, but I just can't seem to get it right. Can you please assist me?

const array = [1, 2, 4, 591, 392, 391, 2, 5, 10, 2, 1, 1, 1, 20, 20];

const dupArray = (arr) => {
  let newArray = array.sort();
  let filteredArray = [];
  for (y = 0; y < newArray.length; y++) {
    for (i = y + 1; i < newArray.length; i++) {
      if (newArray[y] === newArray[i]) {
        filteredArray.push(newArray[i]);
      }
    }
  }

  return filteredArray
};

console.log(dupArray());

javascript

Answer 1

Answer №1

I believe the anticipated outcome will be: [1, 1, 1, 1, 2, 2, 2, 20, 20]

Snippet:

const array = [1, 2, 4, 591, 392, 391, 2, 5, 10, 2, 1, 1, 1, 20, 20]

const dupArray = (arr) => Object
  .entries(arr.reduce((a, c) => (a[c] = ++a[c] || 1, a), {}))
  .filter(e => e[1] > 1)
  .map(e => Array(e[1]).fill(+e[0]))
  .flat(1)

console.log(dupArray(array))

Answer 2

I believe the anticipated outcome will be: [1, 1, 1, 1, 2, 2, 2, 20, 20]

Snippet:

const array = [1, 2, 4, 591, 392, 391, 2, 5, 10, 2, 1, 1, 1, 20, 20]

const dupArray = (arr) => Object
  .entries(arr.reduce((a, c) => (a[c] = ++a[c] || 1, a), {}))
  .filter(e => e[1] > 1)
  .map(e => Array(e[1]).fill(+e[0]))
  .flat(1)

console.log(dupArray(array))

Answer 3

Answer №2

Providing you with the duplicates array to assist you.

const findDuplicates = (inputArray) => {
  let sortedArray = inputArray.slice().sort(); 
  let duplicateValues = [];
  for (let i = 0; i < sortedArray.length - 1; i++) {
    if (sortedArray[i + 1] == sortedArray[i]) {
      duplicateValues.push(sortedArray[i]);
    }
  }
  return duplicateValues;
}

let originalArray = [1, 2, 4, 591, 392, 391, 2, 5, 10, 2, 1, 1, 1, 20, 20];
alert(`Original Array: ${originalArray}, Duplicates: ${findDuplicates(originalArray)}`);

Answer 4

Providing you with the duplicates array to assist you.

const findDuplicates = (inputArray) => {
  let sortedArray = inputArray.slice().sort(); 
  let duplicateValues = [];
  for (let i = 0; i < sortedArray.length - 1; i++) {
    if (sortedArray[i + 1] == sortedArray[i]) {
      duplicateValues.push(sortedArray[i]);
    }
  }
  return duplicateValues;
}

let originalArray = [1, 2, 4, 591, 392, 391, 2, 5, 10, 2, 1, 1, 1, 20, 20];
alert(`Original Array: ${originalArray}, Duplicates: ${findDuplicates(originalArray)}`);

Answer 5

Answer №3

If you're looking to identify duplicates in an array, a simple filter function can do the trick.

const array = [1, 2, 4, 591, 392, 391, 2, 5, 10, 2, 1, 1, 1, 20, 20];

const findDuplicates = (arr) => arr.filter( x => 
  arr.filter(y => y === x).length > 1
).sort()

console.log(findDuplicates(array))

The logic behind this code is as follows:

Iterate through the elements of the array and filter out elements that have more than one occurrence
Sort the resulting array to display duplicate elements in ascending order

Answer 6

If you're looking to identify duplicates in an array, a simple filter function can do the trick.

const array = [1, 2, 4, 591, 392, 391, 2, 5, 10, 2, 1, 1, 1, 20, 20];

const findDuplicates = (arr) => arr.filter( x => 
  arr.filter(y => y === x).length > 1
).sort()

console.log(findDuplicates(array))

The logic behind this code is as follows:

Iterate through the elements of the array and filter out elements that have more than one occurrence
Sort the resulting array to display duplicate elements in ascending order

Answer 7

Answer №4

Presented below are two efficient approaches for sorted arrays. In my analysis, the expected result should be [1,1,1,1,2,2,2,20,20]

const array = [1, 2, 4, 591, 392, 391, 2, 5, 10, 2, 1, 1, 1, 20, 20];

//Implementing the first solution
const dupArray = (arr) => {
  arr = arr.sort((a,b) => a-b);
  let filteredArray = [];
  let currentElement = null;
  for(let i = 0; i < arr.length; i ++){
    if(arr[i] === currentElement){
      filteredArray.push(arr[i]);
    }else{
      currentElement = arr[i];
      if(arr[i] === arr[i+1]){
        filteredArray.push(arr[i]);
      }
    }
  }
  return filteredArray;
};

//Introducing the second solution
const dupArray2 = (arr) => {
  arr = arr.sort((a,b) => a-b);
  for(let i = 0; i < arr.length; i ++){
    if(arr[i] != arr[i-1] && arr[i] != arr[i+1]){
      arr.splice(i,1);
      i -= 1;
    }
  }
  return arr;
};
console.log(dupArray(array));
console.log(dupArray2(array));

Answer 8

Presented below are two efficient approaches for sorted arrays. In my analysis, the expected result should be [1,1,1,1,2,2,2,20,20]

const array = [1, 2, 4, 591, 392, 391, 2, 5, 10, 2, 1, 1, 1, 20, 20];

//Implementing the first solution
const dupArray = (arr) => {
  arr = arr.sort((a,b) => a-b);
  let filteredArray = [];
  let currentElement = null;
  for(let i = 0; i < arr.length; i ++){
    if(arr[i] === currentElement){
      filteredArray.push(arr[i]);
    }else{
      currentElement = arr[i];
      if(arr[i] === arr[i+1]){
        filteredArray.push(arr[i]);
      }
    }
  }
  return filteredArray;
};

//Introducing the second solution
const dupArray2 = (arr) => {
  arr = arr.sort((a,b) => a-b);
  for(let i = 0; i < arr.length; i ++){
    if(arr[i] != arr[i-1] && arr[i] != arr[i+1]){
      arr.splice(i,1);
      i -= 1;
    }
  }
  return arr;
};
console.log(dupArray(array));
console.log(dupArray2(array));

Answer 9

Answer №5

Initially, I implemented a custom sorting function within array.sort() to achieve an ascending order. I introduced a boolean flag called hasDuplicates to track if duplicates have been encountered previously. If not, the element is duplicated and added to the array. To prevent re-processing of elements, I assigned y as i-1.

From an efficiency standpoint, this approach efficiently linearly traverses the array only once.

const array = [1, 2, 4, 591, 392, 391, 2, 5, 10, 2, 1, 1, 1, 20, 20];

const dupArray = (arr) => {
  let newArray = array.sort((a, b) => a - b);  
  let filteredArray = [];
  for (y = 0; y < newArray.length; y++) {
    let hasDuplicates = false;                
    for (i = y + 1; i < newArray.length; i++) {
      if (newArray[y] === newArray[i]) {    
        filteredArray.push(newArray[i]); 
        if(!hasDuplicates) {               
          filteredArray.push(newArray[i]);
          hasDuplicates = true;
        }
      } else {
        y = i - 1;
        break;
      }
    }
  }

  return filteredArray
};

console.log(dupArray());

Answer 10

Initially, I implemented a custom sorting function within array.sort() to achieve an ascending order. I introduced a boolean flag called hasDuplicates to track if duplicates have been encountered previously. If not, the element is duplicated and added to the array. To prevent re-processing of elements, I assigned y as i-1.

From an efficiency standpoint, this approach efficiently linearly traverses the array only once.

const array = [1, 2, 4, 591, 392, 391, 2, 5, 10, 2, 1, 1, 1, 20, 20];

const dupArray = (arr) => {
  let newArray = array.sort((a, b) => a - b);  
  let filteredArray = [];
  for (y = 0; y < newArray.length; y++) {
    let hasDuplicates = false;                
    for (i = y + 1; i < newArray.length; i++) {
      if (newArray[y] === newArray[i]) {    
        filteredArray.push(newArray[i]); 
        if(!hasDuplicates) {               
          filteredArray.push(newArray[i]);
          hasDuplicates = true;
        }
      } else {
        y = i - 1;
        break;
      }
    }
  }

  return filteredArray
};

console.log(dupArray());

moving all duplicate elements in an array into a separate array

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Similar questions

Adding functions to the prototype of a function in JavaScript

Styling Javascript Objects

I attempted to publish my React application using gh-pages and encountered the following error: "The argument for 'file' must be a string. However, it was received as undefined."

Utilize Object literal manipulation to include properties in a specific sequence

At times, Vue.js may encounter difficulties when attempting to load a component

Encountering an issue in Typescript where utilizing ref in ShaderMaterial triggers an error stating: "The anticipated type is originating from the property 'ref' declared within the 'PolygonMat' type definition."

Unable to retrieve values from JSON objects within an array

Instead of storing the result in a variable, return the value directly in Angular2

In certain Express app files, the use of Sequelize modules may result in a return value of undefined

Is there a way for me to determine the quality of a video and learn how to adjust it?

Encountering 'Unacceptable' error message when attempting to retrieve response via AJAX in the SPRING

What is the best way to optimize performance by transferring data efficiently from a database?

Get a Google Sheets file in CSV format

Data entry and a dropdown menu

Select a user at random from the reactions in the message

Is it possible to filter a single field for two different values in a relationMapping using Objection.js?

Combining Express.js-REST-Endpoint with a Meteor Application

Encountering an Assertion Error when attempting to import a custom package in Angular 13

Security ExpoStore malfunctioning (React Native, TypeScript)

In JavaScript, using square brackets before a method allows for dynamic method