Merge pull request #163 from jsca-kwok/jk-days

Number of days algorithm

DIRECTORY.md

@@ -116,6 +116,7 @@
 
 ## Other
   * [Fisher Yates](https://github.com/TheAlgorithms/Ruby/blob/master/other/fisher_yates.rb)
+  * [Number of Days](https://github.com/TheAlgorithms/Ruby/blob/master/other/number_of_days.rb)
 
 ## Project Euler
   * Problem 1

other/number_of_days.rb

@@ -0,0 +1,35 @@
+# Challenge name: Number of Days Between Two Dates
+#
+# Write a program to count the number of days between two dates.
+#
+# The two dates are given as strings, their format is YYYY-MM-DD as shown in the examples. 
+# Example 1:
+# Input: date1 = "2019-06-29", date2 = "2019-06-30"
+# Output: 1
+#
+# Example 2:
+# Input: date1 = "2020-01-15", date2 = "2019-12-31"
+# Output: 15
+#
+# Constraints: The given dates are valid dates between the years 1971 and 2100.
+
+
+#
+# Approach 1: Using Ruby built-in Date.parse
+# Time complexity: O(1)
+# Space complexity: O(1)
+#
+
+require 'date'
+
+def number_of_days(date1, date2)
+  beginning_date = Date.parse(date1)
+  end_date = Date.parse(date2)
+  (end_date - beginning_date).to_i.abs
+end
+
+puts number_of_days("2019-06-29", "2019-06-30")
+# => 1
+
+puts number_of_days("2020-01-15", "2019-12-31")
+# => 15