diff --git a/data_structures/hash_table/fizz_buzz.rb b/data_structures/hash_table/fizz_buzz.rb
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+++ b/data_structures/hash_table/fizz_buzz.rb
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+# Write a program that outputs the string representation of numbers
+# from 1 to n. But for multiples of three it should output “Fizz”
+# instead of the number and for the multiples of five output “Buzz”.
+# For numbers which are multiples of both three and five output
+# “FizzBuzz”.
+
+#
+# Approach 1: Hash it!
+#
+
+# Intuition
+#
+# This approach is an optimization over approach 2. When the
+# number of mappings are limited, approach 2 looks good. But What
+# if you decide to add too many mappings?
+#
+# Having a condition for every mapping is not feasible or may be
+# we can say the code might get ugly and tough to maintain.
+#
+# What if tomorrow we have to change a mapping or maybe delete
+# a mapping? Are we going to change the code every time we have a
+# modification in the mappings?
+#
+# We don't have to. We can put all these mappings in a Hash Table.
+
+# Complexity Analysis
+
+# Time Complexity: O(N)
+# Space Complexity: O(1)
+
+# @param {Integer} n
+# @return {String[]}
+def fizz_buzz(n)
+  str = []
+  fizz_buzz = {}
+  fizz_buzz[3] = "Fizz"
+  fizz_buzz[5] = "Buzz"
+
+  n.times do |i|
+    i += 1
+    num_str = ""
+
+    fizz_buzz.each do |key, value|
+      num_str += value if i % key == 0
+    end
+
+    num_str = i.to_s if num_str == ""
+
+    str.push(num_str)
+  end
+
+  str
+end
+
+n = 15
+puts(fizz_buzz(n))