Validate Brackets

Problem Statement:
    Given a sequence of brackets, validate if the sequence is valid.

Solution:
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We all must have solved this problem during college as common application of stack for solving mathematical expressions. Below is the implementation to validate given sequence of brackets.

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import java.util.HashMap; import java.util.Map; import java.util.Stack; /** * Given an sequence of brackets , confirm if sequence is valid * @author PRATEEK */ public class ValidateBrackets { private static Map<Character,Character> hash = new HashMap<>(); static { hash.put('{','}'); hash.put('[',']'); hash.put('(',')'); } /** * Sub-routine to validate the sequence of brackets * @param s * @return */ public static boolean validate(String s){ char[] arr = s.toCharArray(); Stack<Character> stack = new Stack<>(); for(Character c:arr) { switch (c) { case '[': case '{': case '(': stack.push(c); break; case ']': case '}': case ')': { if(hash.values().contains(c)) { if(!stack.isEmpty() && hash.get(stack.peek())==c) stack.pop(); else if(stack.isEmpty()) return false; } } break; default: break; } } return stack.isEmpty(); } public static void main(String[] args) { String s= "{()}[]"; boolean isValid = validate(s); System.out.println("input: "+s); System.out.println("output: " +isValid); } }

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