JavaScript - Modifying repeating numbers in an array

Question

JavaScript - Modifying repeating numbers in an array

I have a list of numbers that repeats multiple times like this;

numbers = [2,3,1,2,1,3,3,1,2]

My goal is to increase each repeated number by 10 every time it appears. Therefore, the updated list should look like this;

updated_numbers = [2,3,1,12,11,13,23,21,22]

It's important to note that the order of the numbers in the list must stay the same.

This example only shows a small portion of the actual list, which contains repetitive sequences of numbers.

If you have any suggestions on how to achieve this task efficiently, I would greatly appreciate it.

javascript arrays

Answer 1

Answer №1

To calculate the final results, simply create a lookup table that counts the frequency of each number in the list. Then, multiply the frequency by 10 and add it to the original number.

const numbers = [4,7,2,8,2,7,7,2,4],
      countMap = {},
      finalResult = numbers.map(num => {
        countMap[num] = (countMap[num] || 0) + 1;
        return num + (countMap[num] - 1) * 10;
      });
console.log(finalResult);

Answer 2

To calculate the final results, simply create a lookup table that counts the frequency of each number in the list. Then, multiply the frequency by 10 and add it to the original number.

const numbers = [4,7,2,8,2,7,7,2,4],
      countMap = {},
      finalResult = numbers.map(num => {
        countMap[num] = (countMap[num] || 0) + 1;
        return num + (countMap[num] - 1) * 10;
      });
console.log(finalResult);

Answer 3

Answer №2

One way to achieve this is by following these steps:


var numbers = [8,9,7,8,7,9,9,7,8];
var countMap = {};

numbers.forEach(function(num, idx) {
    if(countMap[num]) {
        numbers[idx] = num + (10 * countMap[num]);
        countMap[num] = countMap[num] + 1;
    } else {
        countMap[num] = 1;
    }
});

Answer 4

One way to achieve this is by following these steps:


var numbers = [8,9,7,8,7,9,9,7,8];
var countMap = {};

numbers.forEach(function(num, idx) {
    if(countMap[num]) {
        numbers[idx] = num + (10 * countMap[num]);
        countMap[num] = countMap[num] + 1;
    } else {
        countMap[num] = 1;
    }
});

Answer 5

Answer №3

To create a more concise version, you can use a closure to keep track of counting by assigning zero to unknown properties and incrementing the value.

const
    list = [2, 3, 1, 2, 1, 3, 3, 1, 2],
    result = list.map((o => v => v + 10 * (o[v] ??= 0, o[v]++))({}));

console.log(...result);

Answer 6

To create a more concise version, you can use a closure to keep track of counting by assigning zero to unknown properties and incrementing the value.

const
    list = [2, 3, 1, 2, 1, 3, 3, 1, 2],
    result = list.map((o => v => v + 10 * (o[v] ??= 0, o[v]++))({}));

console.log(...result);

JavaScript - Modifying repeating numbers in an array

Answer №1

Answer №2

Answer №3

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