"Discovering the missing numbers in an array using JavaScript - a step-by-step guide

Question

"Discovering the missing numbers in an array using JavaScript - a step-by-step guide

I have a series of numbers in a string, such as "3 -1 0 5". My goal is to create another string that lists the missing numbers from the original sequence once it has been sorted. For example, if the original array is sorted as [-1, 0, 3, 5], then the missing numbers would be [1, 2, 4].

I want to find an efficient solution using modern JavaScript techniques, beyond just using methods like split, parse, and sort. I am looking to utilize concepts like looping through a range of numbers with min..max, checking for certain conditions such as index -1, and adding elements using push.

javascript arrays algorithm numbers

Answer 1

Answer №1

By arranging the original string array, one can easily identify any missing elements within the specified range.

Utilizing a pointer (arrIndex) enhances the efficiency of solving this issue with a time complexity of n (post-sorting) and just a single pass through the array.

let numbers = "3 -1 0 5".split(' ').map(Number);
numbers.sort((a, b) => a - b);

let missingNumbers = [];
let arrIndex = 0;

for (let num = numbers[0]; num < numbers[numbers.length - 1]; num++) {
  if (numbers[arrIndex] === num) {
    arrIndex++;
  } else {
    missingNumbers.push(num);
  }
}

console.log(missingNumbers.join(' '));

Answer 2

By arranging the original string array, one can easily identify any missing elements within the specified range.

Utilizing a pointer (arrIndex) enhances the efficiency of solving this issue with a time complexity of n (post-sorting) and just a single pass through the array.

let numbers = "3 -1 0 5".split(' ').map(Number);
numbers.sort((a, b) => a - b);

let missingNumbers = [];
let arrIndex = 0;

for (let num = numbers[0]; num < numbers[numbers.length - 1]; num++) {
  if (numbers[arrIndex] === num) {
    arrIndex++;
  } else {
    missingNumbers.push(num);
  }
}

console.log(missingNumbers.join(' '));

Answer 3

Answer №2

If you're only interested in the missing numbers, you can avoid sorting by utilizing Math.min(...arr) and Math.max(...arr) as your loop condition to get the missing values.

var str = "3 -1 0 5";

function findMissingNumbers(str){
  var arr = str.split(/\s/);
  var missingNums = [];
  for(var i=Math.min(...arr); i<Math.max(...arr); i++){
     if(arr.indexOf(i.toString()) === -1){
       missingNums.push(i);
     }
  }
  return missingNums;
}
console.log(findMissingNumbers(str));

Answer 4

If you're only interested in the missing numbers, you can avoid sorting by utilizing Math.min(...arr) and Math.max(...arr) as your loop condition to get the missing values.

var str = "3 -1 0 5";

function findMissingNumbers(str){
  var arr = str.split(/\s/);
  var missingNums = [];
  for(var i=Math.min(...arr); i<Math.max(...arr); i++){
     if(arr.indexOf(i.toString()) === -1){
       missingNums.push(i);
     }
  }
  return missingNums;
}
console.log(findMissingNumbers(str));

Answer 5

Answer №3

You can break down the problem by using split, map, sort, reduce, and a while loop to handle missing elements. Afterwards, you can join the missing parts together.

function findMissingValues(string) {
    return string
        .split(' ')
        .map(Number)
        .sort((a, b) => a - b)
        .reduce((result, value, index, array) => {
            var lastValue = array[index - 1];
            if (!index) {
                return result;
            }
            while (++lastValue !== value) {
                result.push(lastValue);
            }
            return result;
        }, [])
        .join(' ');
}

console.log(findMissingValues('3 -1 0 5'));

A slightly shorter version without the need for a while loop

function findMissingValues(string) {
    return string
        .split(' ')
        .map(Number)
        .sort((a, b) => a - b)
        .reduce((result, value, index, array) =>
            (last => result.concat(Array.from({ length: value - last - 1 }, _ => ++last)))(array[index - 1]),
            []
        )
        .join(' ');
}

console.log(findMissingValues('3 -1 0 5'));

Answer 6

You can break down the problem by using split, map, sort, reduce, and a while loop to handle missing elements. Afterwards, you can join the missing parts together.

function findMissingValues(string) {
    return string
        .split(' ')
        .map(Number)
        .sort((a, b) => a - b)
        .reduce((result, value, index, array) => {
            var lastValue = array[index - 1];
            if (!index) {
                return result;
            }
            while (++lastValue !== value) {
                result.push(lastValue);
            }
            return result;
        }, [])
        .join(' ');
}

console.log(findMissingValues('3 -1 0 5'));

A slightly shorter version without the need for a while loop

function findMissingValues(string) {
    return string
        .split(' ')
        .map(Number)
        .sort((a, b) => a - b)
        .reduce((result, value, index, array) =>
            (last => result.concat(Array.from({ length: value - last - 1 }, _ => ++last)))(array[index - 1]),
            []
        )
        .join(' ');
}

console.log(findMissingValues('3 -1 0 5'));

Answer 7

Answer №4

Utilizing the filter method in conjunction with map functions can be beneficial.

let numbers =  "3 -1 0 5 -3 7".split(' ').map(Number);
numbers.sort((a, b) => a-b);
missingNumbers = Array.from({length: numbers[numbers.length-1] - numbers[0] + 1}, 
                        (_, idx) => numbers[0] + idx)
               .filter(element => !numbers.includes(element));
console.log(missingNumbers);

Answer 8

Utilizing the filter method in conjunction with map functions can be beneficial.

let numbers =  "3 -1 0 5 -3 7".split(' ').map(Number);
numbers.sort((a, b) => a-b);
missingNumbers = Array.from({length: numbers[numbers.length-1] - numbers[0] + 1}, 
                        (_, idx) => numbers[0] + idx)
               .filter(element => !numbers.includes(element));
console.log(missingNumbers);

Answer 9

Answer №5

function findMissingNumbers(str) {

    const sortedArray = str.split(' ').map(Number).sort((a,b) => a - b);

    const [minimum, maximum] = [sorted[0], sorted[sorted.length - 1]];

    const missingNumbersArr = Array.from({length:Math.abs(maximum-minimum)}, (_,i) => i + minimum).filter(item => sorted.indexOf(item) === -1);

    return missingNumbersArr.join(' ');
}

const inputString = "3 -1 0 5"
const resultNumbers = findMissingNumbers(inputString);

console.log(resultNumbers);

Answer 10

function findMissingNumbers(str) {

    const sortedArray = str.split(' ').map(Number).sort((a,b) => a - b);

    const [minimum, maximum] = [sorted[0], sorted[sorted.length - 1]];

    const missingNumbersArr = Array.from({length:Math.abs(maximum-minimum)}, (_,i) => i + minimum).filter(item => sorted.indexOf(item) === -1);

    return missingNumbersArr.join(' ');
}

const inputString = "3 -1 0 5"
const resultNumbers = findMissingNumbers(inputString);

console.log(resultNumbers);

"Discovering the missing numbers in an array using JavaScript - a step-by-step guide

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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