How to compare 1 string against multiple strings?

[PricklyPoo]

Ok, I am a beginner at c++ and I cannot figure out the best way to compare a string to multiple strings....

Basically I want something to do this:

1. User enters name such as John Doe, but I want it to not matter if they type it in uppercase, lowercase, etc.

2. Name is checked against multiple strings such as...(john doe) (John Doe) (JOHN DOE)

3. if the name the user enters matches one of those the result is 0, or something similar.

What is the best way to do this? Is there a way that I could just type one string to compare it to the name the user enters instead of every possibility? So I need a way to compare it disregarding the uppercase, lowercase....I think.

Thanks for any help!

Also, I can never think of any programs to make for practice, is there a website with some ideas?

[a8ball]

  PricklyPoo said:

Ok, I am a beginner at c++ and I cannot figure out the best way to compare a string to multiple strings....

Basically I want something to do this:

1. User enters name such as John Doe, but I want it to not matter if they type it in uppercase, lowercase, etc.

2. Name is checked against multiple strings such as...(john doe) (John Doe) (JOHN DOE)

3. if the name the user enters matches one of those the result is 0, or something similar.

What is the best way to do this? Is there a way that I could just type one string to compare it to the name the user enters instead of every possibility? So I need a way to compare it disregarding the uppercase, lowercase....I think.

Thanks for any help!

Also, I can never think of any programs to make for practice, is there a website with some ideas?

Take the string and change it to all upper or all lower then compare once.

[PricklyPoo]

  a8ball said:

Take the string and change it to all upper or all lower then compare once.

But what happens if the user enters JoHn dOE....

[a8ball]

  PricklyPoo said:

But what happens if the user enters JoHn dOE....

You take the string "JoHn dOE" convert to all upper = "JOHN DOE" then comare. If all you want to do is verify that john doe was typed regardless of case then change the case of the string and compare to match. If you have to compare against a certain case (John Doe is different then john doe) then you need multiple compares.

[IceBreakerG]

It doesn't matter. It changes the entire string to upper case. If you do that, like a8ball said, you can just compare 1 time instead of doing it multiple times.

[PricklyPoo]

  a8ball said:

You take the string "JoHn dOE" convert to all upper = "JOHN DOE" then comare. If all you want to do is verify that john doe was typed regardless of case then change the case of the string and compare to match. If you have to compare against a certain case (John Doe is different then john doe) then you need multiple compares.

  IceBreakerG said:

It doesn't matter. It changes the entire string to upper case. If you do that, like a8ball said, you can just compare 1 time instead of doing it multiple times.

Oh, I see now, thanks!

[PricklyPoo]

I just tried to make a quick program but I must be doing a lot wrong since I am getting errors, please help! :p

#include<iostream>
#include <cctype>
#include<string>
using namespace std;

int main()
{

	char johndoe[] = "john doe";
	char name[50];

	cout << "Please Enter Your First And Last Name.\n" << endl;

	cin.getline(name, 50, '\n');

	name=tolower(name);

   if (strcmp(johndoe, name) = 0 ){

	cout << "You Are John Doe.\n";
	}
	else {
		 cout << "You Are Not John Doe.";
		 }
	return 0;
}

[saiz66]

What errors were you getting?

[PricklyPoo]

  saiz66 said:

What errors were you getting?

Mainly things about converting a char to int......On this line

name=tolower(name);

[cykosis]

tolower will only work on chars, so if you want to convert the string, you need to do it in a loop using the str.length() to find the number of iterations

[spacey]

Hi Prickly,

Some problems, tolower seems to expect one character, and it returns an int.

http://www.cplusplus.com/reference/clibrar...pe/tolower.html

So you need to loop through each character in your name (you know the number of times you have to loop by checking the length of your string), and convert them one by one.

[PricklyPoo]

Thanks for the help!

I am just really having a hard time understanding this. :(

I tried to just use the code on that cplusplus website and replace it with my variables but it didn't work. :/

#include<iostream>
#include <cctype>
#include<string>
using namespace std;

int main()
{
	int i=0;
	char johndoe[] = "john doe";
	char name[50];

	cout << "Please Enter Your First And Last Name.\n" << endl;

	cin.getline(name, 50, '\n');

	while (johndoe[i])
	{
		  name=johndoe[i];
		  putchar (tolower(name));
		  i++;
		  }


   if (strcmp(johndoe, name) = 0 ){

	cout << "You Are John Doe.\n";
	}
	else {
		 cout << "You Are Not John Doe.";
		 }
	return 0;
}

It just comes up with the char to int problem and incompatible types in assignment of `char' to `char[50] messages.

So I need to just do them one by one and keep looping? Isn't there a better way? What if I wanted to compare multiple strings, I would have to do a loop for each one then?

[rpgfan]

You can also make it a bit more complex and make use of the <algorithm> header:

#include <iostream>
#include <string>
#include <algorithm>
#include <cctype>

int main ()
{
	std::string x = "John Doe";

	// transform(iterator start, iterator finish, iterator initialResultPosition, UnaryFunction op);
	// initialResultPosition - where to start storing the result for each iteration
	// (it is automatically incremented each iteration)
	// op - a pointer to a function
	std::transform(x.begin(), x.end(), x.begin(), toupper);
	std::cout << x << std::endl;
}

If you need more info, feel free to check out cplusplus.com's entry on the transform algorithm or cppreference.com's entry on the transform algorithm (or both). Note that cppreference keeps things simple. cplusplus.com prefers to give examples, and specify a LOT more on the page, which can make it difficult to figure out what you need to read.

Edit:

If you want to still do it without the algorithm, here it is:

for (int i = 0; i < someString.length(); i++)
	someString[i] = toupper(someString[i]);

Edited January 26, 2008 by rpgfan

[PricklyPoo]

Thanks rpg, I used the second code you posted and it works.

#include<iostream>
#include <cctype>
#include<string>
#include <algorithm>
using namespace std;

int main()
{

	string x = "john doe";
	string y;

	cout << "Please Enter Your First And Last Name.\n" << endl;

	getline(cin, y, '\n');

   for (int i = 0; i < y.length(); i++)
	y[i] = tolower(y[i]);

   if (strcmp (x,y) == 0);
   {
			  cout << "You Are John Doe.";

   cin.get();
}

The only problem is strcmp, it says I need two const chars, does that mean I have to save the results of the tolower function to chars somehow and then run strcmp?

[rpgfan]

You shouldn't need to use strcmp. You can just use the '==' operator when you use C++ strings. :)

However, if you really needed to use strcmp, you would use strcmp(x.c_str(), y.c_str()). The c_str member function returns a C-string, a null-terminated array of chars.

[PricklyPoo]

  rpgfan said:

You shouldn't need to use strcmp. You can just use the '==' operator when you use C++ strings. :)

However, if you really needed to use strcmp, you would use strcmp(x.c_str(), y.c_str()). The c_str member function returns a C-string, a null-terminated array of chars.

Hehe oh, ok.

Works perfectly now thanks!

#include<iostream>

using namespace std;

int main()
{

	string x = "john doe";
	string y;

	cout << "Please Enter Your First And Last Name.\n" << endl;

	getline(cin, y, '\n');

   for (int i = 0; i < y.length(); i++)
	y[i] = tolower(y[i]);

   if ( x == y )
   {
			  cout << "You Are John Doe.";
			  }
   else 
   {
		cout << "You Are Not John Doe.";
		}

   cin.get();
}

Here it is if anyone other beginner ever needs it as a reference. :p

[rpgfan]

Oh, and I should note that the loop should actually use an unsigned integer, not a signed integer, which is the default if no signed/unsigned specifier is...specified.

The reason for this is because the length member function returns a size. Obviously, you can have a zero-length (empty) string, but you can't go any lower than 0, which is why it should be unsigned. In fact, gcc complains about comparing a signed value (the loop variable) with an unsigned value (x.length()).

Happy coding! :)

[Aeonandromere]

Quickly threw this together. Untested - but should work.

#include <iostream>
#include <string>

int main()
{
	std::string name;
	std::string nameCompare = "John Doe";

	std::cout << "Enter name: ";
	getline(std::cin, name);

	if (name.compare(nameCompare) == 0)
	{
		std::cout << "identical" << std::endl;
	}
	else
	{
		std::cout << "not identical" << std::endl;
	}
}

EDIT: Nevermind, didn't see that you wanted to check for varying cases.