02CS140 Midterm Exam. February 17, 2011. James S. Plank

Answers and grading

Question #1: The answer is: G: iss.str(argv[1]); iss >> i;

Grading: 2 points

Question #2: The answer is: A: cin >> i;

Grading: 2 points

Question #3: The proper way to write this is to have it return a double, since an average is a floating point quantity. Its input should be a reference to a vector of ints, so that the vector is not copied when the procedure is called. Thus, the answer is B.

Grading: 3 points. 1.5 points for answering D.

Question #4: The answer is: C: Because that way, users of the class cannot mess with the data.

Grading: 3 points.

Question #5: This will print the value 14 in hexadecimal. Its value in hex is 0xe. However, the printf() statement does not put the "0x" in front of the value. Instead, it pads it to two characters with leading zeros printed. Thus, the answer is: P: 0e.

Grading: 3 points. 2 points for answering S. 1.5 points for answering Q. 1 point for answering O, R or T, 0.5 points for answering A, V or J.

Question #6: D: iss.clear(); iss.str(s); if (iss >> i) cout << i << endl;

Grading: 3 points. 1.5 points for answering F. 1 point for answering E.

Question #7: E: Before any code: typedef vector <double> DVec; Then: vector <DVec> dv;

Grading: 3 points.

Question #8: D: 5 5 5 5 5 1 10 10 11 11

If you want to test it, it is in: q08.cpp.

Grading: 3 points. 1.5 points for answering H. 1 point for answering F.

Question #9: H: printf("%-30s %5d\n", s.c_str(), i).

Grading: 3 points. 1 point for answering B, D, F, G, O or P.

Question #10: cs and argv[1] point to the same C-style string. s1 and s2 are each copies. Thus, cs and argv[1] will point to "XBC." s1 will be "AYC" and s2 will be "ABCZ." The output is: 

UNIX> q10 ABC
XBC
XBC
AYC
ABCZ
UNIX>
If you want to test it, it is in: q10.cpp.

Grading: 4 points, allocated as follows:

Questions 11 and 12: Trace though these if you didn't get this correct. I went over this in class. If you want to test them, they are in q11.cpp and q12.cpp. 
UNIX> q11
A
CC
ECE
GCEG
ICEGI
UNIX> q12
CC
ECE
GCEG
ICEGI
ICEGI
UNIX>

Grading: 4 points each.

Question #13: Straightforward use of stringstreams and the find method: 

#include <vector>
#include <sstream>
#include <iostream>
using namespace std;

vector <int> i_like_tea(string &s)
{
  istringstream ss;
  vector <int> rv;
  int i;
  string str;

  ss.str(s);
  i = 0;
  while (ss >> str) {
    if (str.find('t') != string::npos || str.find('T') != string::npos) rv.push_back(i);
    i++;
  }
  return rv;
}

The program in this directory, q13.cpp also has a main() that lets you test it.

Grading: 9 points, allocated as follows: