C++ Startup

1. Write a function that takes two string objects, and returns true if the second is a prefix of the first, and false otherwise. Your function should not call find() or rfind(). Write a main function to test your startsWith function.
bool startsWith(string s, string pre) {

2. Write a reverse() function that takes a string, and returns a new string that is its reverse. E.g.,
reverse("bark") should return the string object representation of "krab". Write a main function to test your reverse function.
string reverse(string s) {

3. Given the following statements:
string s = "abcde";
string t = "";
What is the value of:
a) t.length()    b) s.replace(0, 2, 'x')    c) s[3]    d) s.at(2)    e) s.substr(1)    f) s.substr(3, 8)    g) s.substr(1, 1)  

What is the output?
t += 'A';
cout << t;

4. What's the output?

void mystery(int & a, int & b, int c) {
   c += a + b;
   b += a + c;
   a *= 2;
}

int main() {
   int i = 1;
   int j = 2;
   int k = 3;
   mystery(k, i, j);
   cout << i << " " << j << " " << k << endl;
}

5. Write a C++ function repeat that takes a non-negative integer rep and a string s, and returns a string that contains rep copies of s. This is a codestepbystep.com problem. Write a main function that tests your repeat function.

6. Given the function below, what is the output of the call mystery(435)? This is similar to a codestepbystep.com problem.
int mystery(int n) {
   if(n < 10) return n;
   else {
      int a = n / 10;
      int b = n % 10;
      return mystery(a+b);
   }
}

7. Write a recursive function evenDigits that takes an integer n and returns a new integer containing only the even digits from n, in the same order. If n does not contain any even digits, return 0.
evenDigits(43671) returns 46
evenDigits(3517) returns 0

8. Assume you have implemented binary search in a function binarySearch. Assume the following:
int arr[] = {-4, -1, 2, 14, 23, 30, 45, 100, 166, 165, 435, 444, 286, 1000};
Which down the indices of the elements that are compared to the search key when the following call is executed:
int find = binarySearch(arr, 14, 2);
The second argument represents the size of the array.