44 lines
1.5 KiB
Java
44 lines
1.5 KiB
Java
// Author: Rodney Shaghoulian
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// Github: github.com/RodneyShag
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// HackerRank: hackerrank.com/RodneyShag
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import java.util.Scanner;
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import java.util.HashMap;
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import java.util.ArrayDeque;
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// ArrayDeque is "likely to be faster than Stack when used as a stack" - Java documentation
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class Solution {
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public static void main(String[] args) {
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/* Create HashMap to match opening brackets with closing brackets */
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HashMap<Character, Character> map = new HashMap<>();
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map.put('(', ')');
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map.put('[', ']');
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map.put('{', '}');
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/* Test each expression for validity */
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Scanner scan = new Scanner(System.in);
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while (scan.hasNext()) {
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String expression = scan.next();
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System.out.println(isBalanced(expression, map) ? "true" : "false" );
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}
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scan.close();
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}
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private static boolean isBalanced(String expression, HashMap<Character, Character> map) {
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if ((expression.length() % 2) != 0) {
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return false; // odd length Strings are not balanced
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}
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ArrayDeque<Character> deque = new ArrayDeque<>(); // use deque as a stack
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for (int i = 0; i < expression.length(); i++) {
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Character ch = expression.charAt(i);
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if (map.containsKey(ch)) {
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deque.push(ch);
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} else if (deque.isEmpty() || ch != map.get(deque.pop())) {
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return false;
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}
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}
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return deque.isEmpty();
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}
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}
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