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package data_structures.Stacks;

import java.util.Scanner;

import java.util.Stack;

/**

*

* The nested brackets problem is a problem that determines if a sequence of

* brackets are properly nested. A sequence of brackets s is considered properly

* nested if any of the following conditions are true: - s is empty - s has the

* form (U) or [U] or {U} where U is a properly nested string - s has the form

* VW where V and W are properly nested strings For example, the string

* "()()[()]" is properly nested but "[(()]" is not. The function called

* is_balanced takes as input a string S which is a sequence of brackets and

* returns true if S is nested and false otherwise.

*

* @author akshay sharma

* @date: 2017-10-17

* @author <a href="https://github.com/khalil2535">khalil2535<a>

*

*/

class BalancedBrackets {

/**

*

* @param s

* @return

*/

static boolean is_balanced(String s) {

Stack<Character> bracketsStack = new Stack<>();

char[] text = s.toCharArray();

for (char x : text) {

switch (x) {

case '{':

case '<':

case '(':

case '[':

bracketsStack.push(x);

break;

case '}':

if (bracketsStack.peek() == '{') {

bracketsStack.pop();

break;

} else {

return false;

}

case '>':

if (bracketsStack.peek() == '<') {

bracketsStack.pop();

break;

} else {

return false;

}

case ')':

if (bracketsStack.peek() == '(') {

bracketsStack.pop();

break;

} else {

return false;

}

case ']':

if (bracketsStack.peek() == '[') {

bracketsStack.pop();

break;

} else {

return false;

}

}

}

return bracketsStack.empty();

}

/**

*

* @param args

* @TODO remove main method and Test using JUnit or other methodology

*/

public static void main(String args[]) {

try (Scanner in = new Scanner(System.in)) {

System.out.println("Enter sequence of brackets: ");

String s = in.nextLine();

if (is_balanced(s)) {

System.out.println(s + " is balanced");

} else {

System.out.println(s + " ain't balanced");

}

}

}

}