Remove Duplicates from Sorted Array (different final results)

Question

I am new at Programing and learning Javascript by doing some exercises from leetcode.com. I wanted to write a code to remove duplicates in a sorted array. When I use "console.log" at the end of the function to show the final result, I get the expected result. However when I use return (with the same variable) I get a wrong result. Can anybody please tell me, where I went wrong? Hier is my code:

/**
 * @param {number[]} nums
 * @return {number}
 */
var removeDuplicates = function (nums) {
  var newNums = []

  if (nums.length == 0) {
    newNums = []
  }

  for (var i = 0; i < nums.length; i++) {

    var curr = nums[i]
    var next = nums[i + 1]
    if (curr != next) {
      newNums.push(curr)
    }
  }

  console.log(newNums)
  return newNums
};

And here is a picture with the code and the results. the green arrow shows the output of (console.log), and the red one shows the output of (return). Thank you in advance!

Before asking questions here search on google also. here is your answer — Kunal Tanwar
– Kunal Tanwar, Commented Aug 23, 2021 at 8:52
Your code works. If you call the function like this console.log(removeDuplicates([1,2,2,3])) is returns the same thing as the console.log — thetailor.de
– thetailor.de, Commented Aug 23, 2021 at 8:53
btw, if (nums.length == 0) is superfluous. you could exit early but not assign an array, you already have. — Nina Scholz
– Nina Scholz, Commented Aug 23, 2021 at 8:55
Thank you all for your replies. I already have seen multiple Ways on how to solve the problem. But this one i wrote myself. I just want to understand, why i have different results in (return newNums) and consloe.log(newNums), eventhough they are supposed to return the same answer or am i wrong here. — Hamzah
– Hamzah, Commented Aug 23, 2021 at 10:21

Nina Scholz · Accepted Answer · 2021-08-24 07:57:13Z

1

A slightly different approach by keeping the original object reference to the array and mutating the array by copying and adjusting the length of the array.

This approach does not need another array.

It basically checks if the predecessor is unequal to the actual item and copies the item to a new index j. This variable has the final length of the array and truncates the unwanted rest of the array.

function removeDuplicates(array) {
    let j = 0;
    for (let i = 0; i < array.length; i++) {
        if (array[i - 1] !== array[i]) array[j++] = array[i];
    }
    array.length = j;
    return array;
}

console.log(removeDuplicates([0, 1, 1, 2, 2, 2, 2, 3, 4, 5, 5]));

edited Aug 24, 2021 at 7:57

answered Aug 23, 2021 at 16:06

Nina Scholz

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Comments

Abdul Azeem · Accepted Answer · 2021-08-24 09:07:54Z

0

Here's how you can remove duplicates in any(sorted or unsorted) array in Javascript

const removeDuplicates = (orignalArray) =>{
  let allUniqueArray=[];
  let repWordArray=orignalArray.slice();
 
  const removeAnElement=(array, elem)=>{
    const index = array.indexOf(elem);
    if (index > -1) {
      array.splice(index, 1);
    }
    return array;
  }
 
  orignalArray.forEach(elem=>{
    if(!allUniqueArray.includes(elem)){
      allUniqueArray.push(elem);
      repWordArray=removeAnElement(repWordArray,elem)
    }
  });
  return allUniqueArray;
};

let array=[1,2,3,3,4,5,6,6,7];
const uniqueArray = removeDuplicates(array);
console.log('array: ',array);
console.log('uniqueArray: ',uniqueArray);

edited Aug 24, 2021 at 9:07

answered Aug 23, 2021 at 9:07

Abdul Azeem

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3 Comments

Hamzah Over a year ago

Thank you for your help! However the code you have writen removes the duplicated number completly. For example [1,1,1,1] -> it returns [ ]. But, what it should do, is only remove the Duplicates (repetition). The correct answer should be [1].

Abdul Azeem Over a year ago

@Hamzah got your point, I've updated my answer.

Hamzah Over a year ago

Perfect. It works now as it should. Thank you for your time and Help!

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