init

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

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