C++ In code, every { must have a corresponding } Similarly, every [ must have a

Question

C++

In code, every { must have a corresponding }

Similarly, every [ must have a corresponding ] and every ( must have a corresponding )

Furthermore, the symbols must be “appropriately closed” in the sense that they are closed in the reverse of the order that they are opened.

For example:

{[]} is a legal sequence

{[}] is NOT a legal sequence because the } was closed when the [ was the last character that was opened

[[]] is a legal sequence

[{}{}] is a legal sequence

{{{{{{{{{{{{{{{{}}}}}}}}}}}}}}}} is a legal sequence

{ is NOT a legal sequence because the { is never closed

Going further:

   for(int i = 0; i < 10; i++){ cout << i; } is a legal sequence

And so on.

How do I write a program that reads in a .cpp file and determines if the {},[],() are legally sequenced?

Explanation / Answer

/*
C++ Program to check for balanced parentheses in an expression using stack.
Given an expression as string comprising of opening and closing characters
of parentheses - (), curly braces - {} and square brackets - [], we need to
check whether symbols are balanced or not.
*/
#include<iostream>
#include<stack>
#include<string>
using namespace std;
// Function to check whether two characters are opening
// and closing of same type.
bool ArePair(char opening,char closing)
{
   if(opening == '(' && closing == ')') return true;
   else if(opening == '{' && closing == '}') return true;
   else if(opening == '[' && closing == ']') return true;
   return false;
}
bool AreParanthesesBalanced(string exp)
{
   stack<char> S;
   for(int i =0;i<exp.length();i++)
   {
       if(exp[i] == '(' || exp[i] == '{' || exp[i] == '[')
           S.push(exp[i]);
       else if(exp[i] == ')' || exp[i] == '}' || exp[i] == ']')
       {
           if(S.empty() || !ArePair(S.top(),exp[i]))
               return false;
           else
               S.pop();
       }
   }
   return S.empty() ? true:false;
}

int main()
{
   /*Code to test the function AreParanthesesBalanced*/
   string expression;
   cout<<"Enter an expression: "; // input expression from STDIN/Console
   cin>>expression;
   if(AreParanthesesBalanced(expression))
       cout<<"Balanced ";
   else
       cout<<"Not Balanced ";
}

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.