C++ comparing 2 strings

Question

I have the following code:

int compare(string a,string b)
{
    int length=a.length();
    for(int i=0; i < length; i++)
    {
        if(a[i]<b[i])
            return 1;
        if(a[i]>b[i])
            return 0;
    }
    ....
}

I'm interesting in the cases when length of string a is bigger than length of string b and string a starts with string b.
Example:
string a="abcdefghi"
string b="abcde"
The function will return 0. I want to know if there is any chance for this function to return 1; in this conditions.

Written as it is, no. You should also consider `b.length` in the `for` loop. If you find yourself in the condition where one of the strings is over and you still have characters on the other, you know you have to return non-zero. — Federico klez Culloca, Jun 28 '19 at 07:52
[Here](https://stackoverflow.com/questions/34873209/implementation-of-strcmp/34873406)'s a bunch of implementations in C which you can take inspiration from. — Federico klez Culloca, Jun 28 '19 at 07:54
You're invoking undefined behavior, so anything can happen. `b[i]` is undefined when `i >= b.length()` — Sid S, Jun 28 '19 at 08:13
Are you writing your compare function for the sake of it or do you just need to compare two strings? If it's latter case you just can write `a < b`. — sklott, Jun 28 '19 at 08:35
I have a program that has a bug and I'm trying to find it (don't know the cases in which doesn't work and can't find a test where the program doesn't work but I know for sure that it has a bug) so I found this sequence of code and if this function can return 1 in this conditions that means this is one of the bugs. — Ovidiu Firescu, Jun 28 '19 at 08:40
I wonder why you return 0 if a[i]>b[i] - and what about a[i]==b[i]? — JeffRSon, Jun 28 '19 at 08:45
I didn't put the whole function and i just put random numbers on return because is not relevant to the question.I just wanted to know if it's possible to return 1 in this conditions. Here is the whole function https://pastebin.com/vduLJenZ and as you can see length will always have the length of a(pathPrev). — Ovidiu Firescu, Jun 28 '19 at 08:52

score 2 · Accepted Answer · edited Jun 28 '19 at 10:37

2

Total two scenarios are possible:-

if we have the length of b > 0 , then we have to make sure that a[i] ASCII value must be less than b[i] ASCII value..
```
string a="abcdefghi"
string b="abcde"
```
In your example when we reach at index 5, the result would be undefined, means b[5] might contain garbage value whose ASCII value is greater than a[i]. or the result might be vise-versa.

edited Jun 28 '19 at 10:37

JeJo

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answered Jun 28 '19 at 08:34

sha111

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This is the answer I'm looking for, so in some cases in this conditions is possible for the function to return 1, thanks you. Also thanks to @Sid S for pointing out the same thing. – Ovidiu Firescu Jun 28 '19 at 08:43

C++ comparing 2 strings

1 Answers1