Thread: Simple sort

Well I have two data files which are sorted name1 and name2. Then I have to output them into one file name sorted. No arrays or vectors yet at least with this problem or the sort(). We have only had <string> <iostream> <fstream> <iomanip>.

Any Ideas? I have two files data1 and data2 which then need to be combined into one file sorted in alphabetical order. Perhaps that was a better way of saying it. I spent about 3 more hours last night to no avail.

Unless the original files are sorted, you can't sort them without first saving into an array.

IF the original files are sorted then you could do something like:

Code:

read in name1
read in name2
while either file is not empty
   if name1<name2 or 2nd file EOF output name1 and load new name1
   else if name2<name1 or 1st file EOF output name2 and load new name2

If they aren't sorted, you HAVE to load both files completely into an array/vector before you can sort.

The problem with that is as soon as there is a word not in alphabetical order in just keeps repeating the word until infinity. I tried to alter it so it swaps the words but it still repeats.

You talking about my pseudocode? Like I said, if the two files aren't alphabetical to begin with, my code won't work. If they are, post your code and I'll see if I can spot the problem.

Code:

/* 
	
	2. Ordered List
	Description: Program that will combine to lists of data and put them in a sorted order.
	File: main.cxx
	Programmer: ****
	E-mail: ****
	Compiler: g++
	Last modified: 3/29/05
*/
using namespace std;
#include <iostream>
#include <string>
#include <fstream>

int main()
{
	
	string namesOne, // Used to temporarily store a name from the first file
		   namesTwo, // Used to temporarily store a name from the second file
		   temp; // Used to swap the two variables
	
	ifstream inNames1, // Used to input the names from the first file
			 inNames2; // Used to input the names from the second file
	ofstream outNames; // Used to output names to a file
	
	inNames1.open("/Users/****/Documents/School/Rutgers/CS/P4_Luebcke_HOME/merge/names1.data");
	inNames2.open("/Users/****/Documents/School/Rutgers/CS/P4_Luebcke_HOME/merge/names2.data");
	outNames.open("/Users/****/Documents/School/Rutgers/CS/P4_Luebcke_HOME/merge/names.data");
	
	inNames1 >> namesOne;
	inNames2 >> namesTwo;
	
	while(!inNames1 || !inNames2)
	{
		if(namesOne < namesTwo || !inNames2.eof())
		{
			outNames << namesOne << endl;
			inNames1 >> namesOne;
		}
		else if(namesTwo < namesOne || !inNames1.eof())
		{
			outNames << namesTwo << endl;
			inNames2 >> namesTwo;
			temp = namesTwo;
			namesTwo = namesOne;
			namesOne = temp;
		}
		
	}
	
	inNames1.close();
	inNames2.close();
	outNames.close();
	return 0;
}

Ok, i think you are confused on how to tell if a file is EOF. I admit I'm not well versed in file manipulation so someone could easily correct me, but I think eof() returns true when the end is reached, so both

Code:

if(namesOne < namesTwo || !inNames2.eof())

statements need to be changed to

Code:

if(namesOne < namesTwo || inNames2.eof())

Also, I'm not sure if "!inNames1" works the way you expect it to. Change that line to use eof's as well:

Code:

while(!inNames1.eof() || !inNames2.eof())

Also, if you notice, when file1 is eof you are still comparing namesOne to namesTwo, BUT namesOne still has an old name that you never cleared out. If that old name is less than the current namesTwo you'll get an infinite loop. Also be sure to take out the swap you placed in there before retesting.

Great, I can't believe all that trouble because of a ! hehe... Now I just have to figure out why it doesn't input the last two names in both the files.. Thanks a lot for your help PJYelton.