20. Valid Parentheses (#196)

* Create 20.ValidParentheses.py

* Create 20.ValidParentheses.java

* Delete 20.ValidParentheses.py

* Update 20.ValidParentheses.java

* Update README.md

Author: pranav-git-hub

Java/20.ValidParentheses.java

@@ -0,0 +1,16 @@
+//Time Complexity n
+//Space Complexity n
+public boolean isValid(String s) {
+	Stack<Character> stack = new Stack<Character>();
+	for (char c : s.toCharArray()) {
+		if (c == '(')
+			stack.push(')');
+		else if (c == '{')
+			stack.push('}');
+		else if (c == '[')
+			stack.push(']');
+		else if (stack.isEmpty() || stack.pop() != c)
+			return false;
+	}
+	return stack.isEmpty();
+}

README.md

@@ -203,7 +203,7 @@ Check out ---> [Sample PR](https://github.com/codedecks-in/LeetCode-Solutions/pu
 
 | #    | Title                                                                                                               | Solution                                                    | Time   | Space  | Difficulty | Tag                    | Note |
 | ---- | ------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------- | ------ | ------ | ---------- | ---------------------- | ---- |
-| 020  | [Valid Parentheses](https://leetcode.com/problems/valid-parentheses/)                                               | [Python](./Python/20_ValidParentheses.py) [C++](./C++/Vlalid_Parentheses.cpp)                   | _O(n)_ | _O(n)_ | Easy       | Stack                  |      |
+| 020  | [Valid Parentheses](https://leetcode.com/problems/valid-parentheses/)                                               | [Python](./Python/20_ValidParentheses.py) [C++](./C++/Vlalid_Parentheses.cpp)[Java](./Java/20.ValidParentheses.java)                   | _O(n)_ | _O(n)_ | Easy       | Stack                  |      |
 | 084  | [Largest Rectangle in Histogram](https://leetcode.com/problems/largest-rectangle-in-histogram/)                     | [C++](./C++/Largest-Rectangle-in-Histogram.cpp)             | _O(n)_ | _O(n)_ | Hard       | Stack                  |
 | 150  | [Evaluate Reverse Polish Notation](https://leetcode.com/problems/evaluate-reverse-polish-notation/)                 | [Python](./Python/150.EvaluateReversePolishNotation.py) <br> [Java](./Java/evaluate_reverse_polish_notation.java)     | _O(n)_ | _O(1)_ | Medium     | Stack                  |      |
 | 1047 | [Remove All Adjacent Duplicates In String](https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string/) | [C++](./C++/remove-all-adjacent-duplicates-in-string.cpp)   | _O(n)_ | _O(n)_ | Easy       | Stack                  |      |