solves valid parantheses

Author: anishLearnsToCode

README.md

@@ -8,7 +8,7 @@
 | 9 | [PalindromeNumber](https://leetcode.com/problems/palindrome-number/) | Easy | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)](https://github.com/anishLearnsToCode/leetcode-algorithms/blob/master/src/PalindromeNumber.java) |
 | 13 | [Roman To Integer](https://leetcode.com/problems/roman-to-integer/) | Easy | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)](https://github.com/anishLearnsToCode/leetcode-algorithms/blob/master/src/RomanToInteger.java) |
 | 14 | [Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix/) | Easy | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)](https://github.com/anishLearnsToCode/leetcode-algorithms/blob/master/src/LongestCommonPrefix.java) |
-| 2 | []() | Easy | |
+| 20 | [ValidParentheses](https://leetcode.com/problems/valid-parentheses/) | Easy | |
 | 2 | []() | Easy | |
 | 2 | []() | Easy | |
 | 2 | []() | Easy | |

src/ValidParentheses.java

@@ -0,0 +1,48 @@
+// https://leetcode.com/problems/valid-parentheses/
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.Stack;
+
+public class ValidParentheses {
+    private static final Set<Character> openBrackets = new HashSet<>();
+    private static final Map<Character, Character> inverse = new HashMap<>();
+
+    static {
+        openBrackets.add('(');
+        openBrackets.add('{');
+        openBrackets.add('[');
+
+        inverse.put(')', '(');
+        inverse.put('}', '{');
+        inverse.put(']', '[');
+    }
+
+    public boolean isValid(String string) {
+        Stack<Character> brackets = new Stack<>();
+        for(int index = 0 ; index < string.length() ; index++) {
+            char character = string.charAt(index);
+            if (isOpenBracket(character)) {
+                brackets.push(character);
+            } else {
+                if (!brackets.isEmpty() && brackets.peek() == inverse(character)) {
+                    brackets.pop();
+                } else {
+                    return false;
+                }
+            }
+        }
+
+        return brackets.isEmpty();
+    }
+
+    private char inverse(char bracket) {
+        return inverse.get(bracket);
+    }
+
+    private boolean isOpenBracket(char bracket) {
+        return openBrackets.contains(bracket);
+    }
+}