Merge pull request neetcode-gh#1302 from voski/patch-12

Create 0287-Find-The-Duplicate-Number.rb

Author: Ahmad-A0

ruby/287-Find-The-Duplicate-Number.rb

@@ -0,0 +1,23 @@
+# @param {Integer[]} nums
+# @return {Integer}
+def find_duplicate(nums)
+    a = 0
+    b = 0 
+    
+    loop do
+        a = nums[a]
+        b = nums[b]
+        b = nums[b]
+        
+        break if a == b
+    end
+    
+    a = 0
+    loop do
+        a = nums[a]
+        b = nums[b]
+        break if a == b
+    end
+
+    a
+end