Create ValidParentheses.java

Author: 17tanya

Stacks/ValidParentheses.java

@@ -0,0 +1,24 @@
+//LeetCode 20. Valid Parentheses
+//Question - https://leetcode.com/problems/valid-parentheses/
+
+class Solution {
+    public boolean isValid(String s) {
+        Stack<Character> stk = new Stack<>();
+        
+        for(char c : s.toCharArray()){
+            if(c == '(' || c == '[' || c == '{') stk.push(c);
+            else{
+                switch(c){
+                    case ')': if(stk.isEmpty() || stk.pop() != '(') return false;
+                        break;
+                    case ']': if(stk.isEmpty() || stk.pop() != '[') return false;
+                        break;
+                    case '}': if(stk.isEmpty() || stk.pop() != '{') return false;
+                        break;
+                }
+            }
+        }
+        if(stk.isEmpty()) return true;
+        return false;
+    }
+}