CS140 Midterm Page 3

Question 6 - Vectors and Pointers

Below, I have three header files that specify the types L and LVec, and the prototype for a procedure print_LVec(). An LVec is a nested data structure with vector at the top level. The vector contains either lists or pointers to lists, and the lists contain either doubles or pointers to doubles. The procedure print_LVec() is supposed to print out all of the doubles, one per line.

header-1.h 
typedef list <double *> L;
typedef vector <L> LVec;

void print_LVec(LVec &v);
header-2.h 
typedef list <double> L;
typedef vector <L *> LVec;

void print_LVec(LVec &v);
header-3.h 
typedef list <double *> L;
typedef vector <L *> LVec;

void print_LVec(LVec &v);

Below are six implementations of print_LVec(). For each of these implementations, and each header file above, choose one of the multiple choice answers below about how the implementation compiles and runs with the header file:

  1. The implementation compiles correctly with the header file, and they print the doubles correctly without making any extraneous copies of the lists.
  2. The implementation/header compile and print correctly, but they make extra copies of the lists.
  3. The implementation/header compile correctly, but they print something other than the doubles.
  4. The implementation/header do not compile correctly because there are problems in the for loops.
  5. The implementation/header do not compile correctly because there is a problem that is not in a for loop. 
void print_LVec(LVec &v)    // Implementation A 
{
  int i;
  L::iterator lit;
  L *lp;

  for (i = 0; i < v.size(); i++) {
    lp = v[i];
    for (lit = lp->begin(); lit != lp->end(); lit++) {
      cout << *lit << endl;
    }
  }
}

void print_LVec(LVec &v)    // Implementation B 
{
  int i;
  L::iterator lit;

  for (i = 0; i < v.size(); i++) {
    for (lit = v[i].begin(); lit != v[i].end(); lit++) {
      cout << *(*lit) << endl;
    }
  }
}

void print_LVec(LVec &v)    // Implementation C 
{
  int i;
  L::iterator lit;

  for (i = 0; i < v.size(); i++) {
    for (lit = v[i]->begin(); lit != v[i]->end(); lit++) {
      cout << *(*lit) << endl;
    }
  }
}

void print_LVec(LVec &v)    // Implementation D 
{
  int i;
  L::iterator lit;

  for (i = 0; i < v.size(); i++) {
    for (lit = v[i]->begin(); lit != v[i]->end(); lit++) {
      cout << *lit << endl;
    }
  }
}

void print_LVec(LVec &v)    // Implementation E 
{
  int i;
  L::iterator lit;
  L *lp;

  for (i = 0; i < v.size(); i++) {
    lp = v[i];
    for (lit = lp.begin(); lit != lp.end(); lit++) {
      cout << *lit << endl;
    }
  }
}

void print_LVec(LVec &v)    // Implementation F 
{
  int i;
  L::iterator lit;
  L lp;

  for (i = 0; i < v.size(); i++) {
    lp = v[i];
    for (lit = lp.begin(); lit != lp.end(); lit++) {
      cout << *(*lit) << endl;
    }
  }
}