Hackerrank Blocks Solution

.MathJax_SVG_Display {text-align: center; margin: 1em 0em; position: relative; display: block!important; text-indent: 0; max-width: none; max-height: none; min-width: 0; min-height: 0; width: 100%} .MathJax_SVG .MJX-monospace {font-family: monospace} .MathJax_SVG .MJX-sans-serif {font-family: sans-serif} .MathJax_SVG {display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 100%; font-size-adjust: none; text-indent: 0; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0; min-height: 0; border: 0; padding: 0; margin: 0} .MathJax_SVG * {transition: none; -webkit-transition: none; -moz-transition: none; -ms-transition: none; -o-transition: none} .mjx-svg-href {fill: blue; stroke: blue}

Higher order functions are one of the key components of functional programming.

A higher order function is a tool that takes other functions as parameters or returns them as a result.

Blocks are nameless methods that can be passed to another method as a parameter.
Passing a block to a method is a great way of data abstraction.

Blocks can either be defined with a keyword do ... end or curly braces { ... }.

Example:

_{a). Passing a block to a method that takes no parameter}

_CODE

def call_block
    puts "Start of method."
    yield
    puts "End of method."
end 
call_block do 
    puts "I am inside call_block method."
end

_OUTPUT

Start of method.
I am inside call_block method.
End of method.

In this example, a block is passed to the call_block method.
To invoke this block inside the method, we used a keyword, yield.
Calling yield will execute the code within the block that is provided to the method.

_{b). Passing a block to a method that takes one or more parameters.}

_CODE

def calculate(a,b)
    yield(a, b)
end

puts calculate(15, 10) {|a, b| a - b}   

_OUTPUT

5

In this example, we have defined a method calculate that takes two parameters  and .
The yield statement invokes the block with parameters  and , and executes it.

---

Task

You are given a partially complete code. Your task is to fill in the blanks (_______).
The factorial method computes: n! {  x  x  x  }.

Solution in ruby

Approach 1.

def factorial
    yield
end

n = gets.to_i
factorial do 
    puts (1..n).inject(:*)
end

---

Approach 2.

def factorial
    yield
end

n = gets.to_i
factorial do 
    puts (1..n).reduce(:*)
end

---

Approach 3.

def factorial
    yield
end

n = gets.to_i
factorial do 
    puts (1..n).inject(:*)   
end

---