Homework #2

1. for(int x=0, y=0; x < 14; x+=2) {
       y += x;
   }
   
   cout << "x: " << x << "; y: " << y << endl;
   

   1. What does the above code print?
   2. Rewrite this code as a while loop.
   3. Rewrite this code using x++ as the increment operator, and an if statement in the body.

2. std::vector vec;
   std::string s;
   int x, y = 0;
   

   What do the above variables contain?


3. Explain the difference between defining, declaring and initializing a variable.


4. Which of the following are legal variable definitions? (Legal meaning will compile.)

   vector v1(5,"twenty");
   vector v2 = {0,1,2};
   int *iarr = new int[20];
   vector v3(iarr);
   vector v4(v3);
   



5. What is the appropriate use of a header file?

6. std::vector vec(20);
   std::vector::const_iterator viter = vec.begin();
   
   double dbl = 2.0;
   while(viter != vec.end()) {
       *viter = (dbl *= dbl);
       viter++;
   }
   

   There's an issue in the above code, and it won't compile. What is it? Fix it, and then provide the contents of vec after the error has been fixed.



7. int x = 15, y = 20;
   int &z = x;
   int *px = &x, *py = &y, *pz = &z;
   *pz = z + *py;
   z -= 10;
   py = pz;
   *pz = x;
   

   What is in the variables x, y and z after the above code runs?



8. int &mystery(int &a, int b) {
     int c = b;
     b = a;
     a = c;
     return c;
   }
   
   int main() {
     int x = 2, y = 5;
     int z = mystery(x,y);
     return 0;
   }
   

   What are the contents of x, y and z after the above code?

   NOTE: We talked about this question in class (01/17), and I said it was a problem that I'd returned c. This is true: it is going to be a problem, it's bad horrible practice to return a reference to a local variable, BUT it isn't a compiler error, it only results in a warning. z will point to where c was in memory. However, that space can't have been changed by the end of the program. Use that to help you figure it out =)