I can't find the bug in this code

[Nezar]

I'm trying to write a program that return the number of occurrence of a sequence of letters in a string. I'm really confused with what i made up !! help me fix it please. :)

 #include<iostream>
#include<string>

using namespace std;

int main()
{
  string seq; // the string to search for the occurrences
  string s_pat; // the pattern to search for
  char empty[1]=""; 
  int s_pat_size=0;// the length of the search pattern
  int repeat=0; // the number of occurrences
  cout<< " Enter the sequence : \n";
  cin>> seq;
  cout<< " Enter the search pattern : \n";
  cin>> s_pat;
  for(int i=0;;i++)
  {
	  if(s_pat[i]==empty[0]) break;
	  s_pat_size++;
  }
  // counting works !! test code --> cout<<" size of pattern : \n"<<s_pat_size<<endl;
  for(int i=0;;i++)
  {
	  if(seq[i]==empty[0]) break;
	  else if(seq[i]==s_pat[0])
	  {
		  for(int j=0;;j++)
		  {
			  if(seq[i+j]!=s_pat[j]) break;
			  else if(j=s_pat_size-1)
			  {
				  repeat++;
				  break;
			  }
		  }
	  }
	  
  }
  cout<<" The pattern \" "<<s_pat<<" \" occurres  "<<repeat<<" times "<<"in  "<<seq<<endl;

}

[jvqpDjzh]

First of all, why do you need this?
line 10: char empty[1]="";

[Nezar]

1.I need it to check the end of the s_pat(search pattern) to count the number of letters in it // line 19
2.I need it to break the for loop in line 23 // see line 25.

I don't know if this is the right approach or not, that's just what came to my mind at the moment.

[jvqpDjzh]

EDIT: line 19-20: do you know that the class string has a length() function that returns the length of the object?

You can use the function find() of the class std::string to find a substring.
http://www.cplusplus.com/reference/string/string/find/

I have written this function a time ago (and I've just rewritten it again :), try to understand it, and if you find bugs just don't hesitate to tell me:

bool itOccurs(std::string str1, std::string str2)
//str2 is the string you want to see if there is in str1
{
    unsigned occurrences = 0;

    for(int i=0; i<str1.length(); i++)
    {
        if(str1[i] == str2[0])
        {
            ++occurrences;
            for(int j = i+1, n = 1; j<str1.length(); n++, j++)
            {
                if(str1[j] != str2[n]) break;
                else occurrences++;
            }
            if(str2.length() == occurrences) return true;
        }
        occurrences = 0;
    }
    return false;
}

(EDIT: I admit, I don't know how to call this function)

[a k n]

Here you go , I've commented what/why I've changed it.

#include<iostream>
#include<string>

using namespace std;

int main()
{
  string seq; // the string to search for the occurrences
  string s_pat; // the pattern to search for
  //no need ot these:
  //char empty[1]=""; 
  //int s_pat_size=0;// the length of the search pattern
  int repeat=0; // the number of occurrences
  cout<< " Enter the sequence : \n";
  cin >> seq;
  cout<< " Enter the search pattern : \n";
  cin >> s_pat;
  /*No need of this either,even if using c-style strings,we have strlen() in string.h
  for(int i=0;;i++)
  {
	  if(s_pat[i]==empty[0]) break;
	  s_pat_size++;
  }
  */
  for(int i = 0; i < seq.size(); ++i)
  {
	  //if(seq[i]==empty[0]) break;
	  if(seq[i] == s_pat[0])
	  {
		  int j=0;
		  while(seq[i+j]==s_pat[j] && j < s_pat.size() && i+j < seq.size() )
                      ++j;
		  if(j == s_pat.size())
			++repeat;
	  }
	  
  }
  cout<<" The pattern \" "<<s_pat<<" \" occurres  "<<repeat<<" times "<<"in  "<<seq<<endl;

}

[Nezar]

Hey guys,
Thank u for the solutions, it worked.
To be honest, i didn't know that "string" is a class, i thought it was a type like "int".
I'm kinda new to C++ and i haven't got to the Classes part of the book I'm studying !! :)
Anyway I really appreciate your help, i learned a lot. :)