Micro Coding Challenges - with solutions

Mastering these coding challenges may not get you a job at google... but you'll be one step closer to understanding coding and building your first JavaScript game at codeguppy.com

These coding challenges are intended for beginners, therefore the solutions are implemented using only simple / classical programming elements. Each solution is accompanied by an online link that helps you quickly run it in a code playground at codeguppy.com

Note: The online code is making use of the codeguppy specific function println() to print the results. This helper function has a similar syntax with console.log()

Coding challenge #1: Print numbers from 1 to 10

https://codeguppy.com/code.html?mrgCtLGA90Ozr0Otrs5Z

for(var i = 1; i <= 10; i++)
{
    console.log(i);
}

Coding challenge #2: Print the odd numbers less than 100

https://codeguppy.com/code.html?eDLA5XPp3bPxP79H2jKT

for(var i = 1; i <= 100; i += 2)
{
    console.log(i);
}

Coding challenge #3: Print the multiplication table with 7

https://codeguppy.com/code.html?fpnQzIhnGUUmCUZy1fyQ

for(var i = 1; i <= 10; i++)
{
    var row = "7 * " + i + " = " + 7 * i;
    console.log(row);
}

Coding challenge #4: Print all the multiplication tables with numbers from 1 to 10

https://codeguppy.com/code.html?78aD4mWSCzoNEVxOQ8tI

for(var i = 1; i <= 10; i++)
{
    printTable(i);
    console.log("");
}

function printTable(n)
{
    for(var i = 1; i <= 10; i++)
    {
        var row = n + " * " + i + " = " + n * i;
        console.log(row);
    }
}

Coding challenge #5: Calculate the sum of numbers from 1 to 10

https://codeguppy.com/code.html?Vy6u9kki2hXM4YjsbpuN

var sum = 0;

for(var i = 1; i <= 10; i++)
{
    sum += i;
}

console.log(sum);

Coding challenge #6: Calculate 10!

https://codeguppy.com/code.html?IIuJX4gnXOndNu0VrywA

var prod = 1;

for(var i = 1; i <= 10; i++)
{
    prod *= i;
}

console.log(prod);

Coding challenge #7: Calculate the sum of even numbers greater than 10 and less than 30

https://codeguppy.com/code.html?DcOffOyoIArmNZHVNM2u

var sum = 0;

for(var i = 11; i <= 30; i += 2)
{
    sum += i;
}

console.log(sum);

Coding challenge #8: Create a function that will convert from Celsius to Fahrenheit

https://codeguppy.com/code.html?oI5mWm6QIMRjY1m9XAmI

function celsiusToFahrenheit(n)
{
    return n * 1.8 + 32;
}

var r = celsiusToFahrenheit(20);
console.log(r);

Coding challenge #9: Create a function that will convert from Fahrenheit to Celsius

https://codeguppy.com/code.html?mhnf8DpPRqqgsBgbJNpz

function fahrenheitToCelsius(n)
{
    return (n - 32) / 1.8;
}

var r = fahrenheitToCelsius(68);
console.log(r);

Coding challenge #10: Calculate the sum of numbers in an array of numbers

https://codeguppy.com/code.html?TteeVr0aj33ZyCLR685L

function sumArray(ar)
{
    var sum = 0;

    for(var i = 0; i < ar.length; i++)
    {
        sum += ar[i];
    }

    return sum;
}

var ar = [2, 3, -1, 5, 7, 9, 10, 15, 95];
var sum = sumArray(ar);
console.log(sum);

Coding challenge #11: Calculate the average of the numbers in an array of numbers

https://codeguppy.com/code.html?7i9sje6FuJsI44cuncLh

function averageArray(ar)
{
    var n = ar.length;
    var sum = 0;

    for(var i = 0; i < n; i++)
    {
        sum += ar[i];
    }

    return sum / n;
}

var ar = [1, 3, 9, 15, 90];
var avg = averageArray(ar);

console.log("Average: ", avg);

Coding challenge #12: Create a function that receives an array of numbers and returns an array containing only the positive numbers

Solution 1:

https://codeguppy.com/code.html?0eztj1v6g7iQLzst3Id3

function getPositives(ar)
{
    var ar2 = [];

    for(var i = 0; i < ar.length; i++)
    {
        var el = ar[i];

        if (el >= 0)
        {
            ar2.push(el);
        }
    }

    return ar2;
}

var ar = [-5, 10, -3, 12, -9, 5, 90, 0, 1];
var ar2 = getPositives(ar);

console.log(ar2);

Coding challenge #12: Create a function that receives an array of numbers and returns an array containing only the positive numbers

Solution 2

https://codeguppy.com/code.html?KefrPtrvJeMpQyrB8V2D

function getPositives(ar)
{
    var ar2 = [];

    for(var el of ar)
    {
        if (el >= 0)
        {
            ar2.push(el);
        }
    }

    return ar2;
}

var ar = [-5, 10, -3, 12, -9, 5, 90, 0, 1];
var ar2 = getPositives(ar);

console.log(ar2);

Coding challenge #12: Create a function that receives an array of numbers and returns an array containing only the positive numbers

Solution 3

https://codeguppy.com/code.html?qJBQubNA7z10n6pjYmB8

function getPositives(ar)
{
    return ar.filter(el => el >= 0);
}

var ar = [-5, 10, -3, 12, -9, 5, 90, 0, 1];
var ar2 = getPositives(ar);
console.log(ar2);

Coding challenge #13: Find the maximum number in an array of numbers

https://codeguppy.com/code.html?THmQGgOMRUj6PSvEV8HD

function findMax(ar)
{
    var max = ar[0];

    for(var i = 0; i < ar.length; i++)
    {
        if (ar[i] > max)
        {
            max = ar[i];
        }
    }

    return max;
}

var ar = [-5, 10, -3, 12, -9, 5, 90, 0, 1];
var max = findMax(ar);
console.log("Max: ", max);

Coding challenge #14: Print the first 10 Fibonacci numbers without recursion

https://codeguppy.com/code.html?rKOfPxHbVwxNWI2d8orH

var f0 = 0;
console.log(f0);

var f1 = 1;
console.log(f1);

for(var i = 2; i < 10; i++)
{
    var fi = f1 + f0;
    console.log(fi);

    f0 = f1;
    f1 = fi;
}

Coding challenge #15: Create a function that will find the nth Fibonacci number using recursion

https://codeguppy.com/code.html?IneuIg9O0rRV8V76omBk

function findFibonacci(n)
{
    if (n == 0)
        return 0;

    if (n == 1)
        return 1;

    return findFibonacci(n - 1) + findFibonacci(n - 2);
}

var n = findFibonacci(10);
console.log(n);

Coding challenge #16: Create a function that will return a Boolean specifying if a number is prime

https://codeguppy.com/code.html?fRYsPEc2vcZTbIU8MKku

function isPrime(n)
{
    if (n < 2)
        return false;

    if (n == 2)
        return true;

    var maxDiv = Math.sqrt(n);

    for(var i = 2; i <= maxDiv; i++)
    {
        if (n % i == 0)
        {
            return false;
        }
    }

    return true;
}

console.log(2, " is prime? ", isPrime(2));
console.log(3, " is prime? ", isPrime(3));
console.log(4, " is prime? ", isPrime(4));
console.log(5, " is prime? ", isPrime(5));
console.log(9, " is prime? ", isPrime(9));

Coding challenge #17: Calculate the sum of digits of a positive integer number

https://codeguppy.com/code.html?RHA714FYio8gWgmjWYPz

function sumDigits(n)
{
    var s = n.toString();
    var sum = 0;

    for(var char of s)
    {
        var digit = parseInt(char);
        sum += digit;
    }

    return sum;
}

var sum = sumDigits(1235231);
console.log("Sum: ", sum);

Coding challenge #18: Print the first 100 prime numbers

https://codeguppy.com/code.html?gnMVeOZXN6VhLekyvui8

printPrimes(100);

// Function prints the first nPrimes numbers
function printPrimes(nPrimes)
{
    var n = 0;
    var i = 2;

    while(n < nPrimes)
    {
        if (isPrime(i))
        {
            console.log(n, " --> ", i);
            n++;
        }

        i++;
    }
}


// Returns true if a number is prime
function isPrime(n)
{
    if (n < 2)
        return false;

    if (n == 2)
        return true;

    var maxDiv = Math.sqrt(n);

    for(var i = 2; i <= maxDiv; i++)
    {
        if (n % i == 0)
        {
            return false;
        }
    }

    return true;
}

Coding challenge #19: Create a function that will return in an array the first "nPrimes" prime numbers greater than a particular number "startAt"

https://codeguppy.com/code.html?mTi7EdKrviwIn4bfrmM7

console.log(getPrimes(10, 100));

function getPrimes(nPrimes, startAt)
{
    var ar = [];

    var i = startAt;

    while(ar.length < nPrimes)
    {
        if (isPrime(i))
        {
            ar.push(i);
        }

        i++;
    }

    return ar;
}

// Returns true if a number is prime
function isPrime(n)
{
    if (n < 2)
        return false;

    if (n == 2)
        return true;

    var maxDiv = Math.sqrt(n);

    for(var i = 2; i <= maxDiv; i++)
    {
        if (n % i == 0)
        {
            return false;
        }
    }

    return true;
}

Coding challenge #20: Rotate an array to the left 1 position

https://codeguppy.com/code.html?MRmfvuQdZpHn0k03hITn

var ar = [1, 2, 3];
rotateLeft(ar);
console.log(ar);

function rotateLeft(ar)
{
    var first = ar.shift();
    ar.push(first);
}

Coding challenge #21: Rotate an array to the right 1 position

https://codeguppy.com/code.html?fHfZqUmkAVUXKtRupmzZ

var ar = [1, 2, 3];
rotateRight(ar);
console.log(ar);

function rotateRight(ar)
{
    var last = ar.pop();
    ar.unshift(last);
}

Coding challenge #22: Reverse an array

https://codeguppy.com/code.html?GZddBqBVFlqYrsxi3Vbu

var ar = [1, 2, 3];
var ar2 = reverseArray(ar);
console.log(ar2);

function reverseArray(ar)
{
    var ar2 = [];

    for(var i = ar.length - 1; i >= 0; i--)
    {
        ar2.push(ar[i]);
    }

    return ar2;
}

Coding challenge #23: Reverse a string

https://codeguppy.com/code.html?pGpyBz0dWlsj7KR3WnFF

var s = reverseString("JavaScript");
console.log(s);

function reverseString(s)
{
    var s2 = "";

    for(var i = s.length - 1; i >= 0; i--)
    {
        var char = s[i];
        s2 += char;
    }

    return s2;
}

## Coding challenge #24: Create a function that will merge two arrays and return the result as a new array

https://codeguppy.com/code.html?vcTkLxYTAbIflqdUKivc

var ar1 = [1, 2, 3];
var ar2 = [4, 5, 6];

var ar = mergeArrays(ar1, ar2);
console.log(ar);

function mergeArrays(ar1, ar2)
{
    var ar = [];

    for(let el of ar1)
    {
        ar.push(el);
    }

    for(let el of ar2)
    {
        ar.push(el);
    }

    return ar;
}

Coding challenge #25: Create a function that will receive two arrays of numbers as arguments and return an array composed of all the numbers that are either in the first array or second array but not in both

https://codeguppy.com/code.html?Y9gRdgrl6PPt4QxVs7vf

var ar1 = [1, 2, 3, 10, 5, 3, 14];
var ar2 = [1, 4, 5, 6, 14];

var ar = mergeExclusive(ar1, ar2);
console.log(ar);

function mergeExclusive(ar1, ar2)
{
    var ar = [];

    for(let el of ar1)
    {
        if (!ar2.includes(el))
        {
            ar.push(el);
        }
    }

    for(let el of ar2)
    {
        if (!ar1.includes(el))
        {
            ar.push(el);
        }
    }

    return ar;
}

Coding challenge #26: Create a function that will receive two arrays and will return an array with elements that are in the first array but not in the second

https://codeguppy.com/code.html?bUduoyY6FfwV5nQGdXzH

var ar1 = [1, 2, 3, 10, 5, 3, 14];
var ar2 = [-1, 4, 5, 6, 14];

var ar = mergeLeft(ar1, ar2);
console.log(ar);

function mergeLeft(ar1, ar2)
{
    var ar = [];

    for(let el of ar1)
    {
        if (!ar2.includes(el))
        {
            ar.push(el);
        }
    }

    return ar;
}

Coding challenge #27: Create a function that will receive an array of numbers as argument and will return a new array with distinct elements

Solution 1

https://codeguppy.com/code.html?OkbtP1ZksGHXwqk7Jh3i

var ar = getDistinctElements([1, 2, 3, 6, -1, 2, 9, 7, 10, -1, 100]);
console.log(ar);

function getDistinctElements(ar)
{
    var ar2 = [];

    for(let i = 0; i < ar.length; i++)
    {
        if (!isInArray(ar[i], ar2))
        {
            ar2.push(ar[i]);
        }
    }

    return ar2;
}

function isInArray(n, ar)
{
    for(let i = 0; i < ar.length; i++)
    {
        if (ar[i] === n)
            return true;
    }

    return false;
}

Coding challenge #27: Create a function that will receive an array of numbers as argument and will return a new array with distinct elements

Solution 2

https://codeguppy.com/code.html?NjGtyQdMP49QiaAkmwpU

var ar = getDistinctElements([1, 2, 3, 6, -1, 2, 9, 7, 10, -1, 100]);
console.log(ar);

function getDistinctElements(ar)
{
    var ar2 = [];

    var lastIndex = ar.length - 1;

    for(let i = 0; i <= lastIndex; i++)
    {
        if (!isInArray(ar[i], ar, i + 1, lastIndex))
        {
            ar2.push(ar[i]);
        }
    }

    return ar2;
}

function isInArray(n, ar, fromIndex, toIndex)
{
    for(var i = fromIndex; i <= toIndex; i++)
    {
        if (ar[i] === n)
            return true;
    }

    return false;
}

Coding challenge #28: Calculate the sum of first 100 prime numbers

https://codeguppy.com/code.html?v0O9sBfnHbCi1StE2TxA

var n = 10;
console.log("Sum of first ", n, " primes is ", sumPrimes(10));

function sumPrimes(n)
{
    var foundPrimes = 0;
    var i = 2;
    var sum = 0;

    while(foundPrimes < n)
    {
        if (isPrime(i))
        {
            foundPrimes++;
            sum += i;
        }

        i++;
    }

    return sum;
}

// Returns true if number n is prime
function isPrime(n)
{
    if (n < 2)
        return false;

    if (n == 2)
        return true;

    var maxDiv = Math.sqrt(n);

    for(var i = 2; i <= maxDiv; i++)
    {
        if (n % i === 0)
        {
            return false;
        }
    }

    return true;
}

Coding challenge #29: Print the distance between the first 100 prime numbers

https://codeguppy.com/code.html?xKQEeKYF1LxZhDhwOH7V

printDistances(100);

// Print distances between the first n prime numbers
function printDistances(n)
{
    var lastPrime = 2;
    var i = lastPrime + 1;
    var foundPrimes = 1;

    while(foundPrimes < n)
    {
        if (isPrime(i))
        {
            console.log(i - lastPrime, "\t", i, " - ", lastPrime);

            foundPrimes++;
            lastPrime = i;
        }

        i++;
    }
}

// Returns true if number n is prime
function isPrime(n)
{
    if (n < 2)
        return false;

    if (n == 2)
        return true;

    var maxDiv = Math.sqrt(n);

    for(var i = 2; i <= maxDiv; i++)
    {
        if (n % i === 0)
        {
            return false;
        }
    }

    return true;
}

Coding challenge #30: Create a function that will add two positive numbers of indefinite size. The numbers are received as strings and the result should be also provided as string.

Solution 1

https://codeguppy.com/code.html?v5A0QBsdHaiAVA2CPN5y

var n1 = "2909034221912398942349";
var n2 = "1290923909029309499";
var sum = add(n1, n2);

console.log(n1, "\n", n2, "\n", sum);

function add(sNumber1, sNumber2)
{
    var s = "";
    var carry = 0;

    var maxSize = Math.max(sNumber1.length, sNumber2.length);

    for(var i = 0; i < maxSize; i++)
    {
        var digit1 = digitFromRight(sNumber1, i);
        var digit2 = digitFromRight(sNumber2, i);

        var sum = digit1 + digit2;

        var digitSum = sum % 10;
        digitSum += carry;
        s = digitSum.toString() + s;

        carry = sum >= 10 ? 1 : 0;
    }

    if (carry > 0)
        s = carry + s;

    return s;
}

function digitFromRight(s, digitNo)
{
    if (digitNo >= s.length)
        return 0;

    var char = s[ s.length - 1 - digitNo ];
    return parseInt(char);
}

Coding challenge #30: Create a function that will add two positive numbers of indefinite size. The numbers are received as strings and the result should be also provided as string.

Solution 2

https://codeguppy.com/code.html?yMQXcPgfrYxuaIxqQmZc

var n1 = "2909034221912398942349";
var n2 = "1290923909029309499";
var sum = add(n1, n2);

console.log(n1);
console.log(n2);
console.log(sum);

function add(sNumber1, sNumber2)
{
    var maxSize = Math.max(sNumber1.length, sNumber2.length);

    var s1 = sNumber1.padStart(maxSize, "0");
    var s2 = sNumber2.padStart(maxSize, "0");

    var s = "";
    var carry = 0;

    for(var i = maxSize - 1; i >= 0; i--)
    {
        var digit1 = parseInt(s1[i]);
        var digit2 = parseInt(s2[i]);

        var sum = digit1 + digit2;

        var digitSum = sum % 10;
        digitSum += carry;
        s = digitSum.toString() + s;

        carry = sum >= 10 ? 1 : 0;
    }

    if (carry > 0)
        s = carry + s;

    return s;
}

Others coding challenges to try on your own:

1. Create a function that will return the number of words in a text
2. Create a function that will capitalize the first letter of each word in a text
3. Calculate the sum of numbers received in a comma delimited string
4. Create a function that returns the number of occurrences of each word inside a text. The return will be an array with objects inside {word, count}
5. Create a function to convert a CSV text to a “bi-dimensional” array
6. Create a function that converts a string to an array of characters
7. Create a function that will convert a string in an array containing the ASCII codes of each character
8. Create a function that will convert an array containing ASCII codes in a string
9. Implement the Caesar cypher
10. Implement the bubble sort algorithm for an array of numbers
11. Create a function to calculate the distance between two points defined by their x, y coordinates
12. Create a function that will return a Boolean value indicating if two circles defined by center coordinates and radius are intersecting
13. Create a function that will receive a bi-dimensional array as argument and a number and will extract as a unidimensional array the column specified by the number
14. Create a function that will convert a string containing a binary number into a number
15. Create a function to calculate the sum of all the numbers in a jagged array (contains numbers or other arrays of numbers on an unlimited number of levels)
16. Find the maximum number in a jagged array of numbers or array of numbers
17. Deep copy a jagged array with numbers or other arrays in a new array
18. Create a function to return the longest word in a string
19. Shuffle an array of strings
20. Create a function that will receive n as argument and return an array of n random numbers from 1 to n. The numbers should be unique inside the array.
21. Find the frequency of letters inside a string. Return the result as an array of arrays. Each subarray has 2 elements: letter and number of occurrences.
22. Calculate Fibonacci(500) with high precision (all digits)
23. Calculate 70! with high precision (all digits)

If you like this kind of challenges, please follow @codeguppy on Twitter where coding challenges and other news are sometimes posted (even in graphical form).

Comments

[naveenkumar337]

Hello,
Create a function that will add two positive numbers of indefinite size. The numbers are received as strings and the result should be also provided as a string.

solution 1

Can you explain to me why using carry(why need to take 1 if sum greater then 10)? and why we have to do mudular division and why need to add digitsum and carry