Making strcmp() case insensitive without using strcmpi() (C++)

Question

I am working a program that searches for a string (in this case a name) in a file. I wanted the program not to be case sensitive but strcmp is. I was thinking to convert bot the file and user input to lowercase. But that would be inefficient. Any other suggestions to overcome this?
This is a fraction of code to just get an idea of the program

    cout << "\n Enter the Guests name: ";
    cin.getline(look_4_person, 256);  //name that is being looked up
    cout << "\n Searching... \n";
    while(!name_file.eof())
    {
        ++place;
        name_file.getline(person,255);
        if(strcmpi (person,look_4_person)==0)
        {
        found=place;   
        }
    }
    cout << "\n" << look_4_person << " is number " << found << 
            " on the list \n";

This is terrible style and `while(!name_file.eof())` even is a bug. You should read up on modern C++ in a good book. — Baum mit Augen, Oct 20 '17 at 16:23
@BaummitAugen Currently I am using Big C++ (2nd Edition) Do you have any suggestions? — O2Addict, Oct 20 '17 at 16:25
https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list — Baum mit Augen, Oct 20 '17 at 16:26

gsamaras · Answer 1 · 2017-10-20T16:34:33.717

2

was thinking to convert bot the file and user input to lowercase. But that would be inefficient. Any other suggestions to overcome this?

To re-think this.

This is a typical way of dealing with case sensitiveness. I mean converting both strings (file name and user input) to lowercase.

This takes O(n), where n = max(filename.size, userInput.size).

As for performance, the filename and the user input are usually tiny data, thus I am pretty sure that converting them to lower case, will be definitely not be the bottleneck of your algorithm.

edited Oct 20 '17 at 16:34

answered Oct 20 '17 at 16:28

gsamaras

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But shouldn't I also lowercase the text file as well? – O2Addict Oct 20 '17 at 16:29
yes @Pouya, but it will not affect the complexity of your code more, check my updated answer please. – gsamaras Oct 20 '17 at 16:34

score 0 · Accepted Answer · answered Oct 29 '17 at 03:01

while(!name_file.eof()){
        ++place;
        name_file.getline(person,256);
        for(i=0; i<200; i++)
      {
        person[i] = tolower(person[i]);  //changes to lower case to compare
      }
        if(strcmp (person,look_4_person)==0){   //compares 
        found=place;                            

        }

Making strcmp() case insensitive without using strcmpi() (C++)

2 Answers2