Add challenge

DIRECTORY.md

@@ -13,6 +13,7 @@
     * [Fizz Buzz](https://github.com/TheAlgorithms/Ruby/blob/master/data_structures/arrays/fizz_buzz.rb)
     * [Get Products Of All Other Elements](https://github.com/TheAlgorithms/Ruby/blob/master/data_structures/arrays/get_products_of_all_other_elements.rb)
     * [Remove Elements](https://github.com/TheAlgorithms/Ruby/blob/master/data_structures/arrays/remove_elements.rb)
+    * [Richest Customer](https://github.com/TheAlgorithms/Ruby/blob/master/data_structures/arrays/richest_customer.rb)
     * [Single Number](https://github.com/TheAlgorithms/Ruby/blob/master/data_structures/arrays/single_number.rb)
     * [Sort Squares Of An Array](https://github.com/TheAlgorithms/Ruby/blob/master/data_structures/arrays/sort_squares_of_an_array.rb)
     * [Two Sum](https://github.com/TheAlgorithms/Ruby/blob/master/data_structures/arrays/two_sum.rb)

data_structures/arrays/richest_customer.rb

@@ -0,0 +1,31 @@
+# Challenge name: Richest Customer
+#
+# You are given an m x n integer grid accounts where accounts[i][j]
+# is the amount of money the i​​​​​​​​​​​th​​​​ customer has in the j​​​​​​​​​​​th​​​​ bank.
+#
+# Return the wealth that the richest customer has.
+# A customer's wealth is the amount of money they have in all
+# their bank accounts. The richest customer is the customer that
+# has the maximum wealth.
+#
+# Example 1:
+# Input: accounts = [[1,2,3],[3,2,1]]
+# Output: 6
+# Explanation:
+# 1st customer has wealth = 1 + 2 + 3 = 6
+# 2nd customer has wealth = 3 + 2 + 1 = 6
+# Both customers are considered the richest with a wealth of 6
+# each, so return 6.
+#
+# Example 2:
+# Input: accounts = [[1,5],[7,3],[3,5]]
+# Output: 10
+# Explanation:
+# 1st customer has wealth = 6
+# 2nd customer has wealth = 10
+# 3rd customer has wealth = 8
+# The 2nd customer is the richest with a wealth of 10.
+#
+# Example 3:
+# Input: accounts = [[2,8,7],[7,1,3],[1,9,5]]
+# Output: 17