Create 20-Valid-Parentheses.java

Author: SharmaTushar1

java/20-Valid-Parentheses.java

@@ -0,0 +1,21 @@
+class Solution {
+    public boolean isValid(String s) {
+        if (s.length()%2!=0) 
+            return false;
+        Stack<Character> stack = new Stack<>();
+        for (int i = 0; i<s.length(); i++) {
+            if (stack.isEmpty() && (s.charAt(i)==')' || s.charAt(i)=='}' || s.charAt(i)==']')) 
+                return false;
+            else {
+                if (!stack.isEmpty()) {
+                    if (stack.peek()=='(' && s.charAt(i)==')') stack.pop();
+                    else if (stack.peek()=='{' && s.charAt(i)=='}') stack.pop();
+                    else if (stack.peek()=='[' && s.charAt(i)==']') stack.pop();
+                    else stack.add(s.charAt(i));
+                }
+                else stack.add(s.charAt(i));
+            }
+        }
+        return stack.isEmpty();
+    }
+}