Java Stack
Problem Statement :
In computer science, a stack or LIFO (last in, first out) is an abstract data type that serves as a collection of elements, with two principal operations: push, which adds an element to the collection, and pop, which removes the last element that was added.(Wikipedia)
A string containing only parentheses is balanced if the following is true: 1. if it is an empty string 2. if A and B are correct, AB is correct, 3. if A is correct, (A) and {A} and [A] are also correct.
Examples of some correctly balanced strings are: "{}()", "[{()}]", "({()})"
Examples of some unbalanced strings are: "{}(", "({)}", "[[", "}{" etc.
Given a string, determine if it is balanced or not.
Input Format
There will be multiple lines in the input file, each having a single non-empty string. You should read input till end-of-file.
The part of the code that handles input operation is already provided in the editor.
Output Format
For each case, print 'true' if the string is balanced, 'false' otherwise.
Solution :
Solution in C :
import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
class Parser{
private static final Map<Character, Character> brackets = new HashMap<Character, Character>();
static {
brackets.put('[', ']');
brackets.put('{', '}');
brackets.put('(', ')');
}
boolean checkParenthesesBalance(String str){
final Stack<Character> stack = new Stack<Character>();
for (int i = 0; i < str.length(); i++) {
if (brackets.containsKey(str.charAt(i))) {
stack.push(str.charAt(i));
} else if (stack.empty() || (str.charAt(i) != brackets.get(stack.pop()))) {
return false;
}
}
return stack.empty();
}
}
class Solution{
public static void main(String []argh){
Parser X=new Parser();
Scanner in = new Scanner(System.in);
while (in.hasNext()) {
System.out.println(X.checkParenthesesBalance(in.next()));
}
}
}
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