This is Part 7 of the 7-part Exercise 6-0. Click here to see the other parts.

Exercise 6-0 (Part 7 / 7)

Relating to section 6.3.2 of the textbook (page 119-120). Building on the previous exercise the author introduces an even better “one-pass extract_fails” program which takes half the time to run in comparison to the “two-pass” version. This version of extract_fails function uses the stable_partition and erase from the <algorithm> directive.

The Project

Note that the project for this exercise is exactly the same as the one shown in my Solution to Exercise 6-0 (Part 6 / 7). Except for one file as follows:

extract_fails.cpp

#include <vector>             // std::vector
#include <algorithm>          // std::remove_copy_if

#include "Student_info.h"
#include "fgrade.h"
#include "pgrade.h"

using std::vector;

// A single-pass solution to extract the failed students
// (S6.3.2/119)
vector<Student_info> extract_fails(vector<Student_info>& students)
{
  vector<Student_info>::iterator iter =
      stable_partition(students.begin(), students.end(), pgrade);

  vector<Student_info> fail(iter, students.end());
  students.erase(iter, students.end());

  return fail;
}

Test Program

Using the same set of student grades as per Exercise 6-0 (Part 6 / 7), the result is the same as expected.

pete 100 100 100 100 100
jon 90 90 0 0 0
mary 50 50 50 50 50
anna 40 40 0 0 0
gary 80 80 0 80 0
bob 100 100 100 0 0
ken 20 88 99 44 66
jay 99 39 40 80 0
bill 20 88 0 39 0
^Z
^Z
These students have passed.
bob (60)
ken (65.6)
pete (100)
These students have failed.
anna (24)
bill (39.2)
gary (48)
jay (51.4)
jon (54)
mary (50)

Reference