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I´m working on a homework project and am stuck with this function. I need to solve the problem twice, using <vector> and <set>. We just need to eliminate repeating elements from a vector that´s being passed on as an argument.

This was my first attempt. 

vector<int> erase_repeating_elem(vector<int> s) {
    int len = s.size();
    for (int i = 0; i < len -1; i++) {
        for (int j = i + 1; i < len; j++) {
            if (s[i] == s[j]){
                s.erase (s.begin()+j);
                len--;
            }
        }
    }
    return s;
}

main(){
    vector<int> s = {1, 1, 2, 2, 3, 3};
    s = erase_repeating_elem(s);
    std::cout << "myvector contains:";
    for (unsigned i=0; i<s.size(); ++i)
        std::cout << ' ' << s[i];
    std::cout << '\n';
    return 0;
}

When I tried to run it, i get this: Process returned -1073741819 <0xC0000005>

I thought it might be a memory problem when I erase a vector element as i don´t know if s.size() is calculated again. So i tried this:

vector<int> erase_repeating_elem(vector<int> s) {
    int len = s.size();
    for (int i = 0; i < len -1; i++) {
        for (int j = i + 1; i < len; j++) {
            if (s[i] == s[j]){
                s.erase (s.begin()+j);
                len--;
            }
        }
    }
    return s;
}

I get the same error code. I´m thinking other ways of solving this, maybe swapping repeated elements to the back of the vector an then just using pop_back(). But I think my solution, if it works, is better.

I´m using a cygwin tool-chain on Code::Blocks, but i´m unable to make the debugger run. Any tips on that?

Also, what would be the correct way to approach it in the <set> case? I´m guessing just adding the elements to a new set and let it take care itself of the repeating ones.

thank you.

Santiago
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  • In this loop for (int j = i + 1; i < len; j++) in the condition there is used the variable i instead of j. – Vlad from Moscow Aug 22 '19 at 11:27
  • A `set` is already unique, no duplicates there. I expect you want to write out the code in entirety yourself because this is an assignment? Otherwise you could use this idiom: `v.erase(std::unique(v.begin(), v.end()), v.end());` – Tanveer Badar Aug 22 '19 at 11:28
  • Thanks Vlad from Moscow, now i get the problems of copy pasting... – Santiago Aug 22 '19 at 11:30
  • are you allowed to use `` ? eg " maybe swapping repeated elements to the back of the vector " is exactly what `std::unique` does. – 463035818_is_not_an_ai Aug 22 '19 at 11:32
  • I dont´t think so, they are only letting us use , and for the whole assigment – Santiago Aug 22 '19 at 11:34
  • @Santiago thats a pity. Learning containers but excluding algorithms is somehow against the spirit of the standard library. One without the other is ok-ish, only together they show their full potential – 463035818_is_not_an_ai Aug 22 '19 at 11:50
  • I guess we will get to that soon. But if not, i´ll sure try to learn it myself – Santiago Aug 22 '19 at 11:59

1 Answers1

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In this loop for (int j = i + 1; i < len; j++) in the condition there is used the variable i instead of j. – Vlad from Moscow 2 mins ago

Credits to Vlad from Moscow for spotting my silly mistake.

Santiago
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