From f99770d17641160dca4d0ddc192f5f82fd2fc235 Mon Sep 17 00:00:00 2001
From: robinsonvs <robinsonvs@gmail.com>
Date: Wed, 20 Oct 2021 23:00:40 -0300
Subject: [PATCH 1/2] add valid parenthesis solution in java

---
 .../valid-parenthesis.java                    | 46 +++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 leetcode/20 - validparenthesis/valid-parenthesis.java

diff --git a/leetcode/20 - validparenthesis/valid-parenthesis.java b/leetcode/20 - validparenthesis/valid-parenthesis.java
new file mode 100644
index 0000000..50a2ee3
--- /dev/null
+++ b/leetcode/20 - validparenthesis/valid-parenthesis.java	
@@ -0,0 +1,46 @@
+package Algoritms;
+
+import java.util.ArrayDeque;
+import java.util.Deque;
+
+public class ValidParenthesis {
+
+    public static void main(String[] args) {
+
+        System.out.println(isValid("()[]{}")); // true
+        System.out.println(isValid("([)]"));   // false
+        System.out.println(isValid("([{}])")); // true
+    }
+
+    private static boolean isValid(String s) {
+        Deque<Character> stack = new ArrayDeque<>();
+
+        for (int i = 0; i < s.length(); i++) {
+            char item = s.charAt(i);
+
+            if (item == '(' || item == '{' || item == '[') {
+                stack.push(item);
+                continue;
+            }
+
+            if (stack.isEmpty()) {
+                return false;
+            }
+
+            char valid = stack.pop();
+            switch (item) {
+                case ')':
+                    if (valid == '{' || valid == '[') return false;
+                    break;
+                case '}':
+                    if (valid == '(' || valid == '[') return false;
+                    break;
+                case ']':
+                    if (valid == '(' || valid == '{') return false;
+                    break;
+            }
+        }
+
+        return stack.isEmpty();
+    }
+}

From 62b20f15b3a8c2e3bedc33a296d93832bebf3abc Mon Sep 17 00:00:00 2001
From: robinsonvs <robinsonvs@gmail.com>
Date: Thu, 21 Oct 2021 02:15:51 -0300
Subject: [PATCH 2/2] add valid parenthesis solution in scala

---
 .../valid-parenthesis.scala                   | 24 +++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 leetcode/20 - validparenthesis/valid-parenthesis.scala

diff --git a/leetcode/20 - validparenthesis/valid-parenthesis.scala b/leetcode/20 - validparenthesis/valid-parenthesis.scala
new file mode 100644
index 0000000..9e27e17
--- /dev/null
+++ b/leetcode/20 - validparenthesis/valid-parenthesis.scala	
@@ -0,0 +1,24 @@
+package Algoritms
+
+object ValidParenthesis extends App {
+
+  def validSequence(chr: Char, head: Char): Boolean = {
+    chr == ')' && head == '(' || chr == ']' && head == '[' || chr == '}' && head=='{'
+  }
+
+  def isValid(s: String): Boolean = {
+    s.foldLeft(List[Char]()) ((accumulator, chr) => {
+      chr match {
+        case '(' | '{' | '[' => chr :: accumulator
+        case ')' | '}' | ']' => accumulator match {
+          case head :: tail => if (!validSequence(chr, head)) return false else tail
+        }
+      }
+    }).isEmpty
+  }
+
+  println(isValid("()[]{}")) // true
+  println(isValid("([)]")) // false
+  println(isValid("([{}])")) // true
+
+}