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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. final class BalancedParanthesis {
  8.  
  9.     private static final Map<Character, Character> brackets = new HashMap<Character, Character>();
  10.     static {
  11.         brackets.put('[', ']');
  12.         brackets.put('{', '}');
  13.         brackets.put('(', ')');
  14.     }  
  15.  
  16.     private BalancedParanthesis() {};
  17.  
  18.     /**
  19.      * Returns true is parenthesis match open and close.
  20.      * Understands [], {}, () as the brackets
  21.      * It is clients responsibility to include only valid paranthesis as input.
  22.      * A false could indicate that either parenthesis did not match or input including chars other than valid paranthesis
  23.      * 
  24.      * @param str   the input brackets
  25.      * @return      true if paranthesis match.
  26.      */
  27.     public static boolean isBalanced(String str) {
  28.         if (str.length() == 0) {
  29.             throw new IllegalArgumentException("String length should be greater than 0");
  30.         }
  31.         // odd number would always result in false
  32.         if ((str.length() % 2) != 0) {
  33.             return false;
  34.         }
  35.  
  36.         final Stack<Character> stack = new Stack<Character>();
  37.         for (int i = 0; i < str.length(); i++) {
  38.             if (brackets.containsKey(str.charAt(i))) {
  39.                 stack.push(str.charAt(i));
  40.             } else if (stack.empty() || (str.charAt(i) != brackets.get(stack.pop()))) {
  41.                 return false;
  42.             } 
  43.         }
  44.         return true;
  45.     } 
  46.  
  47.     public static void main(String[] args) {
  48.         System.out.println(isBalanced("[["));
  49.     }
  50. }
Success #stdin #stdout 0.07s 380224KB
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Standard input is empty
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true
https://ideone.com/Ed5eiU
language:
Java (HotSpot 12)
created:
10 years ago
visibility:
public

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