For my void function reverse, I have to get a string and reverse it with recursion.
So far, I have
void reverse(string &s)
{
string b = s;
s = s.substr(1) + s.at(0);
}
but it won't work because of the pass by reference requirement for the function. How do I utilize the pass by reference for recursion?
For the record, here's what the function was when I answered:
void reverse(string &s)
{
s = reverse(s.substr(1)) + s.at(0);
}
Multiple problems here:
First you are adding the result of reverse with a char. reverse returns void so this doesn't work. Second, substr creates a new string and passing a temp by reference is asking for trouble. Finally, in recursion, you need an exit condition. As it is, your method is crashing trying to get a substr when length is 1.
Here's a version that works:
void reverse(string &s)
{
if (s.size() == 1)
return;
string sub = s.substr(1);
reverse(sub);
s = sub + s.at(0);
}
What about:
void _reverse(string& s, size_t z0, size_t z1)
{
if (z1 <= z0)
return;
auto aux = s[z0];
s[z0] = s[z1];
s[z1] = aux;
_reverse(s, z0 + 1, z1 - 1);
}
void _reverse(string& s)
{
_reverse(s, 0, s.length() - 1);
}
int main()
{
string x = "hello my friend";
_reverse(x);
cout << x << endl;
}
std::swap to swap the values.
shas no type so the rest of your code is suspect.reversedoes not return a value but you expect it to.reversewithinreverse