HackerRank Java- Stack
A string containing only parentheses is balanced if the following is true: 1. if it is an empty string 2. if A and B are correct, AB is correct, 3. if A is correct, (A) and {A} and [A] are also correct.
Examples of some correctly balanced strings are: "{}()", "[{()}]", "({()})"
Examples of some unbalanced strings are: "{}(", "({)}", "[[", "}{" etc.
Given a string, determine if it is balanced or not.
- import java.util.*;
-
- class Solution {
-
- private static boolean isBalanced(String expression) {
- if ((expression.length() & 1) == 1)
- return false;
-
- char[] brackets = expression.toCharArray();
- Stack<Character> stack = new Stack<>();
- for (char bracket : brackets)
- switch (bracket) {
- case '{':
- stack.push('}');
- break;
- case '(':
- stack.push(')');
- break;
- case '[':
- stack.push(']');
- break;
- default:
- if (stack.empty() || bracket != stack.peek())
- return false;
- stack.pop();
- }
- return stack.empty();
- }
-
- public static void main(String[] argh) {
- Scanner sc = new Scanner(System.in);
-
- while (sc.hasNext()) {
- String expression = sc.next();
- System.out.println(isBalanced(expression) ? "true" : "false");
- }
- sc.close();
- }
- }
