String Strip / Trim in C++

In C++, there is no built-in string trim function, but we can write one using find_first_not_of and find_last_not_of. For this lesson, a trim() helper function has been provided for you:

// trim() removes leading and trailing spaces
string s = "  hello  ";
string result = trim(s);
// result == "hello"

Here is how a trim function works internally:

string trim(const string& s) {
    int start = 0, end = s.size() - 1;
    while (start <= end && s[start] == ' ') start++;
    while (end >= start && s[end] == ' ') end--;
    return s.substr(start, end - start + 1);
}