Java Stack Hackerrank Solution Watch Video: Sample Input {}() ({()}) {}( [] Sample Output true true false true Code: import java.util.*; class Solution{ public static void main(String []argh) { Scanner sc = new Scanner(System.in); while (sc.hasNext()) { String input=sc.next(); System.out.println(valid(input)); } } static boolean valid(String s){ Stack<Character> st = new Stack<>(); for ( int i= 0 ;i<s.length();i++){ char ch = s.charAt(i); if (ch== '(' || ch== '[' || ch== '{' ){ st.push(ch); } else if (st.isEmpty()){ return false ; } else { char top = st.pop(); if ((top== '(' && ch!= ')' ) || (top== '[' && ch!= ']' )|| (top== '{' && ch!=