InterviewBit - Math: FizzBuzz solution and README

Author: Lanh Hoang

Math/fizzbuzz/README.md

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+# FizzBuzz
+
+## Problem:
+Fizzbuzz is one of the most basic problems in the coding interview world. Try to write a small and elegant code for this problem. 
+
+Given a positive integer `A`, return an array of strings with all the integers from `1` to `N`. 
+
+But for multiples of `3` the array should have "Fizz" instead of the number. 
+
+For the multiples of `5`, the array should have "Buzz" instead of the number. 
+
+For numbers which are multiple of `3` and `5` both, the array should have "FizzBuzz" instead of the number.
+
+Look at the example for more details.
+
+Example:
+
+**Input:**
+```
+A = 5
+```
+
+**Output:**
+```
+[1 2 Fizz 4 Buzz]
+```
+
+## Approach:
+
+While iterating from `1` to `N`, you need to check the following conditions in sequence:
+
+-Check whether the number is divisible by `3` and `5`, if that is the case, print "FizzBuzz".
+
+-Check whether the number is divisible by `3`, in that case, print "Fizz".
+
+-Next, check whether the number is divisible by `5`, in that case print "Buzz".
+
+-Otherwise, print the number.
+
+Time Complexity: `O(N)`
+Space Complexity: `O(N)`

Math/fizzbuzz/fizzbuzz.rb

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+# https://www.interviewbit.com/problems/fizzbuzz
+
+class Solution
+  # @param a : integer
+  # @return an array of strings
+  def fizzBuzz(a)
+    res = []
+    1.upto(a).each do |num|
+      if num % 3 == 0 && num % 5 == 0
+        res.push('FizzBuzz')
+      elsif num % 3 == 0
+        res.push('Fizz')
+      elsif num % 5 == 0
+        res.push('Buzz')
+      else
+        res.push(num)
+      end
+    end
+    res
+  end
+end
+
+class Solution
+  # @param a : integer
+  # @return an array of strings
+  def fizzBuzz(a)
+    (1..a).map do |n|
+      str = ''
+      str += 'Fizz' if n % 3 == 0
+      str += 'Buzz' if n % 5 == 0
+      str.empty? ? n : str
+    end
+  end
+end
+
+a = 5
+p Solution.new.fizzBuzz(a)