CODEWITHSUNDEEP
c++stringsubstring
MAREY
MAREY

Reputation: 51

C++ substring why does it do that?

I am trying to reverse order of a string 5 characters from end of string to beginning For example, if the input was "11111000002222233333", I want output to be "33333222220000011111"

string reverse(string str)
    {
        string tmp = "";
        for(int i = str.length(); i >= 5; i = i - 5)
        {
            tmp.append(str.substr(i - 5, i));
        }
        return tmp;
    };

lets just say that my input was "1000001010000000000010100" but it returns "101000000010100000000000010100010100000010000"

Upvotes: 0

Views: 71

Answers (1)

Rost
Rost

Reputation: 9089

According to documentation:

Returns a substring [pos, pos+count). If the requested substring extends past the end of the string, or if count == npos, the returned substring is [pos, size()).

std::string substr(size_type pos = 0, size_type count = npos) const;

Your mistake is that you treat substr() second parameter as position index. But it's substring length, not end position.

Quick fix is tmp.append(str.substr(i - 5, 5));

Upvotes: 1

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