From 7bdcf9a6b7ab419d37bac256df13c78c12fbdc9e Mon Sep 17 00:00:00 2001
From: "Ahmed M. Abd EL-latif" <ahmed.abdelatife@gmail.com>
Date: Tue, 28 Dec 2021 21:36:06 +0200
Subject: [PATCH] init

---
 Longest Common Prefix.rb | 20 ++++++++++++++++++++
 valid-parentheses.rb     | 20 ++++++++++++++++++++
 2 files changed, 40 insertions(+)
 create mode 100644 Longest Common Prefix.rb
 create mode 100644 valid-parentheses.rb

diff --git a/Longest Common Prefix.rb b/Longest Common Prefix.rb
new file mode 100644
index 0000000..f5fb730
--- /dev/null
+++ b/Longest Common Prefix.rb	
@@ -0,0 +1,20 @@
+def longest_common_prefix(strs)
+    return "" if strs.nil? || strs.size == 0
+    
+    return strs[0] if strs.size == 1
+  
+  output = ""
+  
+  for i in 0...strs[0].size do
+    for j in 1...strs.size do
+      if strs[j][i] != strs[0][i]
+        output = strs[0][0...i]
+        return output
+      end
+    end
+    output << strs[0][i]
+  end
+  
+  output
+  
+end
diff --git a/valid-parentheses.rb b/valid-parentheses.rb
new file mode 100644
index 0000000..850c044
--- /dev/null
+++ b/valid-parentheses.rb
@@ -0,0 +1,20 @@
+# @param {String} s
+# @return {Boolean}
+def is_valid(s)
+    return true if s.empty?
+    
+    stack = []
+    s.each_char do |c|
+        case c
+        when '(', '{', '['
+            stack.push(c)
+        when ')'
+            return false if stack.pop() != '('
+        when '}'
+            return false if stack.pop() != '{'
+        when ']'
+            return false if stack.pop() != '['
+        end
+    end
+    return stack.empty?
+end