Using string function help?

[jon smith]

I need to write a program that will let the user input a string and a character to search for. It should output the number of times that character is in the string. I am just having trouble as to how i am supposed to add up the number of times each one is found. Also, i am supposed to start the index at 0 and then change it to 1 past the index of where the character was last found. i know i am (very) new to c++, so any help would be appreciated.

  #include <iomanip>
#include <cmath>
#include <iostream>
#include <string>
using namespace std;

main()
{ string str1;
	char search;
	char i;
	int count = 0;

	
	cout<<"This program will let the user input a string and then find a character in that string"<<endl;
	cout<<"Please input a string"<<endl<<endl;

	getline(cin, str1);
		cout<<"The string you entered was "<<str1<<endl;
	cout<<"Please input a character to count"<<endl<<endl;
	cin>>search;

	for(i=0, i<int(str1.length()), i++)
	{ str1.find(search,(0));



	}
	cout<<"There are "<<count<<search<<"'s in the string"<<endl;

}

[rozick1]

Typically you would declare the looping variable in the for loop.


The variable i should really be an integer and not a char.

As a beginner you shouldn't start with the std::string functions (such as find). In this case simply increase 'i' in the for loop and check the identity and then increase the count if the identity matches true.

for (int i = 0 ; i < str1.length();i++)
{
           if (str1[i] == search)
                 count++;



}

[jon smith]

well i am in a programming class and we are supposed to use string functions (specifically find). But yes, that way is simpler but i am not supposed to do it that way.

[rozick1]

 #include <iomanip>
#include <cmath>
#include <iostream>
#include <string>
using namespace std;

main()
{ string str1;
	char search;
	char i;
	int count = 0;


	cout<<"This program will let the user input a string and then find a character in that string"<<endl;
	cout<<"Please input a string"<<endl<<endl;

	getline(cin, str1);
		cout<<"The string you entered was "<<str1<<endl;
	cout<<"Please input a character to count"<<endl<<endl;
	cin>>search;

	for(i=0; i<str1.length(); i++)
	{
        int pos_found = str1.find (search,i);

        if (pos_found != string::npos)
        {
            count++; // new char found
            i = pos_found; //start at that character
        }


	}
	cout<<"There are "<<count<<search<<"'s in the string"<<endl;

}

Should do the trick. If you need help understand it then ask.

You should try to look at some simple examples. The for loop components should be separated by a ';' not a ','.

[jon smith]

i have been looking at my book and examples, just wasn't getting it. I think i wasn't setting the equation equal to anything, so i wasn't getting an output. Why does your find(string) equation in line 24 have an i, whilst mine has a 0? Does it make a difference since i is set to start at 0?

[rozick1]

The second parameter to the find function is where the search begins at. This should be i because each time you find a new character then you want to skip to that character + 1 (as you have stated) as opposed to searching from 0 again. If you had 0 in my loop then the program would get stuck in a loop because it would never get past the first matched character.

[jon smith]

Also, what is 'string::npos', i haven't learned that yet.

[rozick1]

http://www.cplusplus.com/reference/string/string/find/

Look at the return value:

If there is a match then the pos of the match.

If no match then a special number (string::npos).

[jon smith]

ok, thanks for explaining that. ill look at that link. Is there a way to do it without using that, though? just wondering.

[rozick1]

Not really. You need to know where there is a match or not. As I said using std::find is overkill for this.

[jon smith]

Yea, i agree that it is overkill too. So i tried to compile it, and when i enter a character for 'search' (i changed to char1 in this actually) and press enter, nothing happens.

#include <iomanip>
#include <cmath>
#include <iostream>
#include <string>

using namespace std;

int main()
{   string str1;
	char char1;
	int i;
	int charcount = 0;
	char pos_found;
	
	cout<<"This program will let the user input a string and then find a character in that string"<<endl;
	cout<<"Please input a string"<<endl<<endl;

	getline(cin, str1);
		cout<<"The string you entered was "<<str1<<endl;
	cout<<"Please input a character to count"<<endl<<endl;
	cin>>char1;

	for(i=0; i<int(str1.length()); i++)
	{ int pos_found = str1.find(char1,(i));

	if (pos_found != string::npos)
		
		charcount++;

	i = pos_found;

	

	}

	
	cout<<"There are "<<charcount<<char1<<"'s in the string"<<endl;
	

	system("pause");
return 0;
}

[rozick1]

I'm not sure why you keep changing the code:

 #include <iomanip>
#include <cmath>
#include <iostream>
#include <string>
using namespace std;

main()
{ string str1;
	char search;
	char i;
	int count = 0;


	cout<<"This program will let the user input a string and then find a character in that string"<<endl;
	cout<<"Please input a string"<<endl<<endl;

	getline(cin, str1);
		cout<<"The string you entered was "<<str1<<endl;
	cout<<"Please input a character to count"<<endl<<endl;
	cin>>search;

	for(i=0; i<str1.length(); i++)
	{
        int pos_found = str1.find (search,i);

        if (pos_found != string::npos)
        {
            count++; // new char found
            i = pos_found;
        }


	}
	cout<<"There are "<<count<<search<<"'s in the string"<<endl;

}

[jon smith]

I had the system pause in there because im going to put a do-while loop in there. It works the first time through after the initial time, but if i try to do it a second run through it exits the program.

#include <iomanip>
#include <cmath>
#include <iostream>
#include <string>

using namespace std;

int main()
{   string str1;
	char char1;
	int i;
	int charcount = 0;
	char pos_found;
	char y = 0;
	char answer;
	
	cout<<"This program will let the user input a string and then find a character in that string"<<endl;
	
	do
	{
	cout<<"Please input a string"<<endl<<endl;

	getline(cin, str1);
		cout<<"The string you entered was "<<str1<<endl;
	cout<<"Please input a character to count"<<endl<<endl;
	cin>>char1;

	for(i=0; i<str1.length(); i++)
	{ int pos_found = str1.find(char1,i);

	if (pos_found != string::npos)
		
		charcount++;

	i = pos_found;

	

	}

	
	cout<<"There are "<<charcount <<char1<<"'s in the string"<<endl;
	cout<<"Do you wish to run this again? y or Y for yes, any other button for no"<<endl;
	cin>>answer;
	}
	while(answer == 'y' || answer == 'Y');
	

}