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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");
}
}
}
}