How to check if particular element in this given array has duplicate?-CodePudding

I might be overthinking or not even close. How can I iterate on this array to check if an element shows up more than one

var myArr = ["88 99 33", "22 88 99", "23 44 88", "77 99 22"];

for(var x in myArr) {
   var currentNum = myArr[x].split(' ');
   // check currentNum if it appears more than once
}

CodePudding user response：

You can add for example a structure (such as Set) to track whether you have a duplicate:

var myArr = ["88 99 33", "22 88 99", "23 44 88", "77 99 22"];

const numbers = new Set();
const duplicates = new Set();

for (let x in myArr) {
    var arrayItem = myArr[x].split(' ');

    for (var y in arrayItem) {
        const currentNumber = arrayItem[y];

        if (numbers.has(currentNumber)) {
            duplicates.add(currentNumber);
        } else {
            numbers.add(currentNumber);
        }
    }
}

console.log([...duplicates]);

Or use a hash map (i.e., an object) or something:

var myArr = ["88 99 33", "22 88 99", "23 44 88", "77 99 22"];

const numbers = {};

for (let x in myArr) {

  var arrayItem = myArr[x].split(' ');

  for (var y in arrayItem) {

    const currentNumber = arrayItem[y];

    // Track number of appearance of current number
    numbers[currentNumber] = numbers[currentNumber] || 0;
    numbers[currentNumber]  ;

  }
}
// Take only items that appeared more than 1
const duplicates = Object.entries(numbers).filter(([key, value]) => (value > 1)).map(([key,]) => key);

console.log(duplicates);

CodePudding user response：

You can flattern the array and then check is the elem is present more than once.

To check if at least one elemet has duplicates, you can use Array#some

flatArr.some(x => checkDuplicates(x)))

const myArr = ["88 99 33", "22 88 99", "23 44 88", "77 99 22"];
const flatArr = myArr.reduce((acc, curr) => {
  currArray = curr.split(" ")
  if (!acc) return [curArray]
  else return acc.concat(currArray)
}, [])

const checkDuplicates = (elem) => flatArr.filter(item => item === elem).length > 2

console.log(checkDuplicates("88"))
console.log(checkDuplicates("23"))

console.log(flatArr.some(x => checkDuplicates(x)))

Note : If you want to add numbers instead of strings, you can map the array to integer as

const flatArr = myArr.reduce((acc, curr) => {
  currArray = curr.split(" ")
  if (!acc) return [curArray]
  else return acc.concat(currArray)
}, []).map(x => parseInt(x))