Problem with iterators - code does not compile

[Claudius7]

Hi, I want to make a function which does the following:
take two strings, str1 and str2. Check if all the characters of one string are contained in the other string. I want to solve this problem using iterators, so here is my code:

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

using namespace std;

bool is_subsequence(string& str1, string& str2)
{
    string tmp;                         // check that str1 is the smaller string, to see if str1 is contained in str2
    if (str1.length() > str2.length())
        {
            tmp = str1;
            str1 = str2;
            str2 = tmp;
        }
        sort(str1.begin(), str1.end()); // sort both strings 
                            // to check if str1 is inside str2 sequentially
        sort(str2.begin(), str2.end());


    typedef string::iterator iter;

    iter j = str2.begin();
    iter i = str1.begin();

    while (i != str1.end())
    {
        j = find(j, str2.end(), *i);
    }
    if (j != str2.end())
        return true;
        return false;
    }

    int main()
    {
    cout << "Please enter two strings " << endl;
    string s1, s2;
    (cin >> s1);
    (cin >> s2);
    cout << "Is s1 contained in s2?? 0=no, 1=yes" <<is_subsequence(s1,s2) <<endl;

    return 0;
    }

The problem is that I enter the two strings and press enter, but the compiler does nothing, i.e. cursor flashes but program doesn't compile nor allows me to do anything so I have just abruptly closed the window... what's going on???

My problem is to figure out if I have played correctly with the iterators and the find function.

[coder777]

The while loop on line 26 will either end immediately (str1.begin() == str1.end()) or never since i will not be changed within the loop. A for loop or range based loop for is better in this case.

Further more the loop should end (maybe with a break) if j == str2.end()

[Claudius7]

Hi coder777, I see. So is it enough to just add "++i" after line 28?

I have done it and now it seems to compile well.

[gunnerfunner]

if (j != str2.end())
        return true;
        return false;
    }

j is never incremented and so this will always return true and it is not clear what is the purpose of this block of code

 string s1, s2;
    (cin >> s1);
    (cin >> s2);

as already mentioned on another thread, this is erroneous and stumbles on whitespace, use getline() instead

cout << "Is s1 contained in s2?? 0=no, 1=yes <<is_subsequence(s1,s2) <<endl;
there's a missing " after "yes" and there is no previous check that s1.size() is <= s2.size(). In fact, as you're trying to

(c)heck if all the characters of one string are contained in the other string

, the string with the larger number of unique (edit: ?) characters should be the parent string and the other string should be the child string and then you check if a child is a sub-set of the parent

[coder777]

So is it enough to just add "++i" after line 28?

Yes.

You should return false within the loop as soon as j -> str2.end(), otherwise you would check the very last character only.

There is a missing " on line 41.

[Claudius7]

Hi coder777, yes, thanks once more. In fact I had already implemented the break instruction within the loop, so the first time that j reached str2.end() the program already stops, avoiding the unnecessary check for all the other characters of str1. Thanks again!