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Coding solutions

Problems and solutions explained and implemented with multiple programming languages

Image for post: Two Sum

Two Sum

Given an array of integers, return indices of the two numbers such that they add up to a specific target.You may assume that each input would have exactly one solution, and you may not use the same element twice.Example:Given nums = [2, 7, 11, 15], target = 9,Because nums[0] + nums[1] = 2 + 7 = 9,re... [...]

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Image for post: Mutliples of 3 and 5

Mutliples of 3 and 5

The problem: If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23. Find the sum of all the multiples of 3 or 5 below 1000.It appears on Project Euler and the solution seems very easy. Maybe it hides some trick or trap but we want to keep the solution and the related... [...]

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Image for post: Singleton: pattern or anti-pattern?

Singleton: pattern or anti-pattern?

Many people consider the singleton an anti-pattern. Many others think it's part of the creational patterns family. I don't care about its definition and I think a singleton can be useful sometimes in the real world! Singleton design pattern is used when you want to have only one instance of a given class. Let's... [...]

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Image for post: Prime Number

Prime Number

Let's find if a number is prime. A prime number (or a prime) is a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers. The first few prime numbers are {2, 3, 5, 7, 11, ….}.Here we have some solutions:PHP: using bcmod and a for loopfunction isPrimeNumber(int $num){ for ($i... [...]

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Image for post: Leap Year

Leap Year

Let's check if a year is a leap year.Rules for determining a Leap YearMost years that can be divided evenly by 4 are leap years. (For example, 2016 divided by 4 = 504: Leap year!)Exception: Century years are NOT leap years UNLESS they can be evenly divided by 400. (For example, 1700, 1800, and 1900 were not leap years, b... [...]

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Image for post: Fibonacci numbers

Fibonacci numbers

Let's see how to print the Fibonacci numbers. The formula expects we will have big numbers so we will be ready to print big numbers without any overflow error. Before showing some code, I want to leave some useful links:Fibonacci on WikipediaFibonacci Number      [...]

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Image for post: Prime Factors

Prime Factors

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Image for post: Factorial


The factorial function (symbol: !) says to multiply all whole numbers from our chosen number down to 1.Examples:4! = 4 × 3 × 2 × 1 = 247! = 7 × 6 × 5 × 4 × 3 × 2 × 1 = 50401! = 1Wikipedia.PHP: using gmp_fact functionA native PHP function called gmp_fact is ava... [...]

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Image for post: Palindrome words

Palindrome words

A palindrome is a word, number, phrase, or other sequences of characters which reads the same backward as forward, such as madam or racecar or the number 10801. Sentence-length palindromes may be written when allowances are made for adjustments to capital letters, punctuation, and word dividers... [...]

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Image for post: FizzBuzz


The FizzFizz buzz is a group word game for children to teach them about division.[1] Players take turns to count incrementally, replacing any number divisible by three with the word "fizz", and any number divisible by five with the word "buzz".Players generally sit in a circle. The player designated to go first says the numb... [...]

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Image for post: Exchange array keys \ values

Exchange array keys \ values

Exchange keys with values and vice-versa from an associative array can be a very common problem. Let's how we can solve it:PHP: Using the array_flip functionThis native function will do the job on the fly!<?phpvar_dump( array_flip( array('a', 'b', 'c') ) );Javascript: using an underscore.js method... [...]

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