How to search file for number type int and write largest and smallest to screen?

[rayborn66]

Hi I need some help.
I am trying to write a program that will search a file for numbers of type int and write the largest and the smallest numbers to the screen. This is how far I got but when I it came to writing the code that would read the file and output the largest and smallest to the screen I kinda uh ...... yeah.

Could someone walk me through how I would do it?

#include <fstream>
#include <iostream>
#include <cstdlib>
using namespace std;

int main()
{
	ifstream fin;
	ofstream fout;

	fin.open("getfromthisfile.txt");
	if(fin.fail())
	{
		cout << "Input file opening failed.\n";
		exit(1);
	}
	
	fout.open("sendtothisfile.txt");
	if(fin.fail())
	{
		cout << "Input file opening failed.\n";
		exit(1);
	}

how I think I should do it ... but most likely will not work...

int next;
	int largest=0;
	int smallest;

	while(! fin.eof())
	{
		next++;
		if(next>largest)
		{
			largest=next;
		}
		fin.get(next);
		fout << "The largest number in getfromthisfile.txt is " << largest <<  endl;
		if(next<smallest)
		{
			smallest=next;
		}
		fin.get(next);
		fout << "The smallest number in getfromthisfile.txt is " << smallest << endl;
	}
	fin.close();
	fout.close();
	system("pause");
	return 0;
}

yeah I am completely new to C++ ... ha :)

[Ancient Dragon]

post the contents of the input file. Does it contain numeric digits only or can it contain non-numeric characters? How to parse the file will depend on what it contains.

[rayborn66]

post the contents of the input file. Does it contain numeric digits only or can it contain non-numeric characters? How to parse the file will depend on what it contains.

Oh yeah sorry about that :) it contains numeric digits only.

[tesuji]

Hello

First, variables must be initialize before using them, e.g. smallest has been defined but never been initialized. So put these two lines just before your while loop:

fin >> next;
smallest = largest = next;

Second, do not use fin.get(next) for this reads one char only, and not an int, result would be DT mismatching. The >> operator is much more powerful for it is overloading with almost all data types of c++, e.g. istream& operator>> (int& val ), just that what you need here.

Third, your while loop starts fine. But inside there is some trouble.

Think of redesign it that way:

while (! fin.eof())  // if you make use of eof(), fin should has been read once at least
{
     // 1. process your just  read-in data here:
     if ( next < smallest ) ...; else; if ( largest < next ) ...;

     // 2. read next data from file 
     fin >> next;  // again, do not use fin.get(.) for data type mismatching
} 

// coming here, smallest and largest shoud contain their appropriate values.
// Sorry, I don't have tested this code, so there might be some minor mistakes.

I hope these hints may help you a little.

-- tesu

[rayborn66]

Awesome, I got it. Thank you :) for the help

:) :) :) :) :) :)
:) :) :) :) :) :)

[Anyzen]

#include <fstream>
#include <iostream>
#include <cstdlib>
#include<limits>
using namespace std;

int main()
{
	ifstream fin;
	ofstream fout;

	fin.open("getfromthisfile.txt");
	if(fin.fail())
	{
		cout << "Input file opening failed.\n";
		exit(1);
	}
	
	fout.open("sendtothisfile.txt");
	if(fin.fail())
	{
		cout << "Output file opening failed.\n";
		exit(1);
	}

	int next;
	int largest=0;
	int smallest;

	fin >> next;
	smallest = largest = next;
	while(! fin.eof())
	{
		
		if ( next < smallest ) 
			smallest=next;

		else if ( largest < next )
			largest=next;

		   fin >> next;
	}
	fout << "The largest number in getfromthisfile.txt is " << largest <<  endl;
	fout << "The smallest number in getfromthisfile.txt is " << smallest << endl;
	fin.close();
	fout.close();

	cin.ignore(numeric_limits<streamsize>::max(),'\n');
	return 0;
}

i kinda followed tesujis advice...and its technically working..given the numbers:

0 1 2 3 4 5 6 7 8 9 10
-1 0 1 2 3 4 5 6 7 8 9
-2 -1 0 1 2 3 4 5 6 7 8
-3 -2 -1 0 1 2 3 4 5 6 7
-4 -3 -2 -1 0 1 2 3 4 5 6
-5 -4 -3 -2 -1 0 1 2 3 4 5
-6 -5 -4 -3 -2 -1 0 1 2 3 4
-7 -6 -5 -4 -3 -2 -1 0 1 2 3
-8 -7 -6 -5 -4 -3 -2 -1 0 1 2
-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0

but when i add a new line lets say, 100 -55 below.. it only reads 100 as largest and not -55 as the smallest..what happened?

is the code wrong? im new to streamfiles....help?

[Emran__]

try copying fin >> next; from the main function and pasting to the while loop, just before the if statement begins.