std::string class find function not returning expected results. I may be using it incorrectly

Question

Using the find method of the string class and I'm not getting the correct results in my query. Here is my code

int main()
{
    string phoneData;
    string name;
    string phoneNumbers[51];
    ifstream inputFile;
    inputFile.open("phonebook");
    int i = 0;
    while (getline(inputFile, phoneData))
    {
        phoneNumbers[i] = phoneData;
        i++;
    }
    cout << "Enter a name or partial name to search for: ";
    getline(cin, name);
    cout << endl << "Here are the results of the search: " << endl;

    for(int i =0;i<50;i++)
    {
        if (name.find(phoneNumbers[i]) == 0)
            cout << phoneNumbers[i] << endl;
    }
    inputFile.close();
    return 0;
}

I would expect that you need to use if(phoneNumbers[i].find(name) != std::string::npos) instead of name.find(phoneNumbers[i]) == 0 — Chad
– Chad, Commented Dec 13, 2012 at 18:01
Hahaha, just somebody. Yeah I'm not sure what happened there but I edited it. Must have been distracted. — Keith
– Keith, Commented Jan 12, 2013 at 6:04

Mike Corcoran · Accepted Answer · 2012-12-13 18:00:47Z

3

you aren't using it correctly. string::find() returns the beginning position when it finds a match, or string::npos if it doesn't find a match. you also have the search backwards. you're looking for 'name' inside 'phoneNumbers[i], not the other way around. your check inside the loop should look like this:

if (phoneNumbers[i].find(name) != string::npos)
    cout << phoneNumbers[i] << endl;

answered Dec 13, 2012 at 18:00

Mike Corcoran

14.6k4 gold badges42 silver badges51 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Keith Over a year ago

Thank you so much. I had a hard time understanding the syntax of this method but now I understand. Thanks again!

Keith Over a year ago

Sorry I was busy with school work. It's finals week! But I didn't forget, I always come back and do the right things. Thanks again for clearing this up.

Dave S · Accepted Answer · 2012-12-13 18:01:32Z

1

Change

if (name.find(phoneNumbers[i]) == 0)

to

if (phoneNumbers[i].find(name) != std::string::npos)

The former is trying to locate phoneNumbers[i] within name. The second (which I believe is what you intended) is searching for name within phoneNumbers[i]. Second, the failure return for std::string::find is std::string::npos not zero.

answered Dec 13, 2012 at 18:01

Dave S

21.2k3 gold badges53 silver badges69 bronze badges

Collectives™ on Stack Overflow

std::string class find function not returning expected results. I may be using it incorrectly

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related