c++ - Interview Question : Trim multiple consecutive spaces from a string

Question

This is an interview question Looking for best optimal solution to trim multiple spaces from a string. This operation should be in-place operation.

input  = "I    Like    StackOverflow a      lot"
output = "I Like StackOverflow a lot"

String functions are not allowed, as this is an interview question. Looking for an algorithmic solution of the problem.

Answer 1

Does using <algorithm> qualify as "algorithmic solution"?

#include <iostream>
#include <string>
#include <algorithm>
#include <iterator>
struct BothAre
{
    char c;
    BothAre(char r) : c(r) {}
    bool operator()(char l, char r) const
    {
            return r == c && l == c;
    }
};
int main()
{
    std::string str = "I    Like    StackOverflow a      lot";
    std::string::iterator i = unique(str.begin(), str.end(), BothAre(' '));
    std::copy(str.begin(), i, std::ostream_iterator<char>(std::cout, ""));
    std::cout << '
';
}

test run: https://ideone.com/ITqxB