Programming Assignment #6- Match Brackets using a Stack: Given a text file, your
ID: 3716221 • Letter: P
Question
Programming Assignment #6- Match Brackets using a Stack:
Given a text file, your program will determine if all the parentheses, braces, and square brackets match, and are nested appropriately. Your program should work for mathematical formulas and most computer programs.
Your program should read in the characters from the file, but ignore all characters except for the following: { } ( ) [ ]
Your program should use the IntStack declaration (IntStack.h), which will be available from Tracs).
The general algorithm is to use a stack to store the opening unmatched brackets. When a closing bracket is encountered, check it against the one on top of the stack-- make sure it matches, and pop it off. When you are finished there should be no unmatched brackets left on the stack.
Input/Output:
Your driver program must prompt the user to enter a filename. It should then try to open the file and then check it to ensure the brackets all match appropriately. If they all match, the program should output a message saying so. If not, the program should output an appropriate error message (there are three possible error messages corresponding to three types of errors shown as follows).
There are three types of errors that can happen (and with any kind of bracket):
missing } : if you reach the end of the file, and there is an opening { that was never matched, like: int main () { x[size]=10;
expected } but found ) : this is a wrong closing bracket, like: {x[i]=10;)...
unmatched } : this occurs if there is a closing bracket but not an opening bracket (not even one of the wrong kind), like: int main () { x[i]=10; } }...
NOTES:
This program must be done in a Linux or Unix environment, using a command line
compiler like g++. Do not use codeblocks, eclipse, or Xcode to compile.
As soon as your driver encounters an error, your program should stop and print out
the appropriate error message. Do NOT try to keep going and find more errors!
The stack is an int stack but you will probably want to put characters on the stack. You can push a character directly on the int stack (it will automatically be converted to an int). When you pop I recommend popping into a char variable first (this will automatically convert the int back into a character).
It might be easier to store the expected closing character on the stack when an opening bracket is encountered. This simplifies the matching when a closing bracket is encountered.
Beware of stack underflow! Do NOT try to pop an empty stack! If you get an error message like this when you run your program: Assertion failed: (!isEmpty())
then you are popping an empty stack: your program should prevent this and output its own appropriate error message instead.
Follow the style guidelines from the Tracs.
Logistics:
For this assignment you need to submit two files: IntStack.cpp and your driver file. Please zip these into one file, assign6_xxxxxx.zip (where xxxxx is your NetID). Then submit the zip file
Submit an electronic copy using the Assignments tool in TRACS before the deadline.
Here is the given file:
Explanation / Answer
code:
#ifndef CHARSTACK_H
#define CHARSTACK_H
class CharStack
{
private:
std::string stackk;
public :
CharStack();
void push(char x);
char pop();
bool checkvalda();
};
#endif
CharStack.cpp
#include <iostream>
#include <conio.h>
#include <iomanip>
#include<string>
#include "CharStack.h"
using namespace std;
CharStack :: CharStack()
{
stackk=" ";
}
void CharStack :: push(char x)
{
stackk+=x;
}
char CharStack :: pop()
{
char lastch=stackk.at(stackk.size()-1);
stackk = stackk.substr(0, stackk.size()-1);
return lastch ;
}
bool CharStack ::checkvalda()
{
if (stackk.size() == 1)
{
return true;
}
else
return false;
}
main.cpp
#include <iostream>
#include <conio.h>
#include<string>
#include <fstream>
#include "CharStack.h"
using namespace std;
int main()
{
int i;
string filna,c;
char a, y, z;
cout<<"enter the file name: ";
cin>>filna;
ifstream filobj (filna);
filobj>>c;
CharStack obj;
for (i = 0; i < c.size(); i++)
{
if ((c[i] == '(') || (c[i] == '{') || (c[i] == '['))
{
obj.push(c[i]);
}
else
{
switch(c[i])
{
case ')':
a = obj.pop();
if ((a == '{') || (a == '['))
{
cout<<"invalid expr!!";
getch();
}
break;
case '}':
y = obj.pop();
if ((y == '[') || (y == '('))
{
cout<<"invalid expr!!";
getch();
}
break;
case ']':
z = obj.pop();
if ((z == '{') || (z == '('))
{
cout<<"invalid expr!!";
getch();
}
break;
}
}
}
bool checkval=obj.checkvalda();
if (checkval == true)
{
cout<<"balanced expr!!";
}
else
{
cout<<"string is not valid.!!";
}
system("pause");
return 0;
}
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