So the problem is, that this code:
string num = "00101011110011100001";
string quartett;
int i = num.length() - 1;
while (i > 0) {
quartett.clear();
quartett = num.substr((i - 3), i);
cout << quartett << endl;
i = i - 4;
}
Prints out this:
0001
11100001
11001110000
1011110
001
actual output should be:
0001
1110
1100
1011
0010
The thing is I don't have any idea why. I hope you can help me and thanks in advance.
The second argument to substr() is length, not index. Should be:
quartett = num.substr((i - 3), 4);
The second parameter in substr is the number of characters you want to print. As you've set that to i, the amount of characters outputted will grow on each iteration.
I think you want to hardcode that to 4.
By the way, your call to quartett.clear(); is pointless as you're assigning it in the following statement.
The substr method
basic_string substr( size_type pos = 0,
size_type count = npos ) const;
takes second parameter as number of characters you want to extract. If this is omitted then the meaning is "to the end of string". Consider example:
std::string a = "0123456789abcdefghij";
std::string sub1 = a.substr(10);
std::cout << sub1 << '\n';
std::string sub2 = a.substr(5, 3);
std::cout << sub2 << '\n';
output:
abcdefghij
567
Thus what you need is quartett = num.substr((i - 3), 4);
use this:
string num = "00101011110011100001";
string quartett;
int no = 4;
int i = num.length();
while (i > 0) {
quartett.clear();
quartett = num.substr((i - no), no);
cout << quartett << endl;
i = i - no;
}
quartettwith thesubstring()call, theclear()is pointless. It cannot be the reason for the problem.