Parenthesis_Checker.cpp

/*
Problem Statement:
------------------
Given an expression string x. Examine whether the pairs and the orders of “{“,”}”,”(“,”)”,”[“,”]” are correct in exp.
For example, the function should return 'true' for exp = “[()]{}{[()()]()}” and 'false' for exp = “[(])”.

Example 1:
----------
Input:
{([])}
Output: 
true
Explanation: { ( [ ] ) }. Same brackets can form balaced pairs, with 0 number of unbalanced bracket.

Example 2:
---------
Input: 
()
Output: 
true
Explanation: (). Same bracket can form balanced pairs, and here only 1 type of bracket is present and in balanced way.

Example 3:
---------
Input: 
([]
Output: 
false
Explanation: ([]. Here square bracket is balanced but the small bracket is not balanced and Hence , the output will be unbalanced.

Your Task: This is a function problem. You only need to complete the function ispar() that takes a string as a parameter and returns a boolean value true if brackets 
are balanced else returns false. The printing is done automatically by the driver code.

Expected Time Complexity: O(|x|)
Expected Auixilliary Space: O(|x|)
*/

// Link --> https://practice.geeksforgeeks.org/problems/parenthesis-checker2744/1#

// Code:
class Solution
{
    public:
    bool ispar(string exp)
    {
        stack <char> s;
        char current;
        
        for(int i=0; i<exp.length(); i++)
        {
            if(exp[i] == '(' || exp[i] == '{' || exp[i] == '[')
            {
                s.push(exp[i]);
                continue;
            }
            
            if(s.empty())
                return false;
                
            switch(exp[i])
            {
                case ')':
                    current = s.top();
                    s.pop();
                    if(current == '{' || current == '[')
                        return false;
                    break;
                
                case '}':
                    current = s.top();
                    s.pop();
                    if(current == '(' || current == '[')
                        return false;
                    break;
                
                case ']':
                    current = s.top();
                    s.pop();
                    if(current == '{' || current == '(')
                        return false;
                    break;
            }
        }
        
        return (s.empty());
    }

};