String Comparison Function.. !!

Question

1.00/5 (2 votes)

See more:

I'm writing a function that compare two c-strings..
unable to complete the function .. please help .. !!
unpredictable output .. !!
i'm doing this .. !!

=> evaluate the length of string 1, and string 2
=> using lesser length as a loop control variable
=> if the strings of same characters then comparing their length.

If i made some modification with the code, gives warning message "not all control paths return value.???"

Please help I'm too much frustrated nOw........

C++

#include <cstring>
#include <iostream>

using namespace std;

int length(char a[])
{
	int temp = 0;
	for (int i = 0; i !='\0' ; i++)
	{
		temp ++;
	}

	return temp;
}

int compare(char a[], char b[])
{
	int a1, a2, var, x;
	a1 = length(a);
	a2 = length(b);
	if (a1 > a2)
	{
		var =  a2;
	}
	else
		var = a1;
	for (int i = 0; i < var; i++)
	{
		if (a[i]==b[i])
		
			x = 0;
		
		else if (a[i]<b[i])
		
			return -1;
		
		else if (a[i]>b[i])
		
			return 1;
		
	}
	if (x==0)
	{
		if (a1>a2)
		
			return 1;
		
		if (a2>a1)

			return -1;

	}
	return x;
}

int main()
{
	char discard;
	const int size = 30;
	char a[size], b[size];
	cin.get(a, size+1);
	cin.get(discard);
	cin.get(b, size+1);
	length(a); length(b);
	cout << compare(a, b);
	system("Pause");
	return 0;
}

Posted 29-Mar-13 2:17am

Usman Hunjra

Add a Solution

Comments

E.F. Nijboer 29-Mar-13 8:55am

Sounds like a school assignment. By the way, what is the logic in using the lesser length when after that it says that only strings of the same length are compared? If you simply write down the requirements in the right order and without contradictions it should be a breeze.

3 solutions

Solution 2

Quote:
=> evaluate the length of string 1, and string 2
=> using lesser length as a loop control variable
=> if the strings of same characters then comparing their length.

C-like strings are zero-terminated, hence you typically don't need to know their length in advance (you could check for '\0' while comparison is in progress).

At each iteration you should stop comparing if:

the corrensponding characters of the two strings are different.

or

one of the two strings terminates (or both of them terminate).

Hence your code might be very compact.

Posted 29-Mar-13 3:10am

CPallini

Updated 29-Mar-13 3:15am

v2

Comments

nv3 29-Mar-13 10:58am

You beat me by a couple of minutes :-)

Solution 3

There are a couple of bugs in your code. I am not going to give you the solution right away, but want you to find it yourself -- that's much more fun. So I am trying to guide you to finding those things.

Function length:
As Style-z pointed out correctly, comparing i with '\0' is not going to help. '\0' will translate into 0 and all you do is compare i == 0. He has already shown the solution, so that is that.

Function compare:
Is there any chance that you leave the for-loop and x NOT being set to 0? (yes, there is! try to figure out in which case that happens). And what value will x have in that case (undefined?).

Your compare function will work, but by far it is not optimal. You will be doing three passes over the strings, one each determining the length and one in the for-loop. Try to do it in one pass; it's possible and the code will be smaller and faster than what you have now.

Function main:
You are again making the same mistake as in your last post. If you tell cin.get that the array a has a size of size+1, get is going to believe that and write past the end of your buffer and destroy other variables! And get is not going to take a newline!

Once you solved all that we might look at making your code readable for others. But that's the next step.

Posted 29-Mar-13 3:28am

nv3

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Style-7 · Accepted Answer · 2013-03-29T02:52:00

Solution 1

see bold text

C#

int length(char a[])
{
    int temp = 0;
    for (int i = 0; a[i] !='\0' ; i++)
    {
        temp ++;
    }

    return temp;
}

Posted 29-Mar-13 2:52am

Style-7

Comments

Usman Hunjra 29-Mar-13 11:52am

nyc ..
thx