exercism/cpp/making-the-grade/making_the_grade.cpp

#include <array>
#include <cstdio>
#include <string>
#include <vector>

// Round down all provided student scores.
std::vector<int> round_down_scores(std::vector<double> student_scores) {
  return std::vector<int>(student_scores.begin(), student_scores.end());
}

// Count the number of failing students out of the group provided.
int count_failed_students(std::vector<int> student_scores) {

  int count{0};

  for (auto score : student_scores) {
    if (score <= 40)
      count++;
  }

  return count;
}

// Determine how many of the provided student scores were 'the best' based on
// the provided threshold.
std::vector<int> above_threshold(std::vector<int> student_scores,
                                 int threshold) {

  std::vector<int> res;

  for (auto score : student_scores) {
    if (score >= threshold)
      res.push_back(score);
  }

  return res;
}

// Create a list of grade thresholds based on the provided highest grade.
std::array<int, 4> letter_grades(int highest_score) {

  int step{(highest_score - 40) / 4};
  std::array<int, 4> grades{41, 0, 0, 0};

  for (int i{1}; i < 4; ++i) {
    grades[i] += grades[i - 1] + step;
  }

  return grades;
}

// Organize the student's rank, name, and grade information in ascending order.
std::vector<std::string>
student_ranking(std::vector<int> student_scores,
                std::vector<std::string> student_names) {

  std::vector<std::string> res;
  int rank = 1;

  for (int i{0}; i < student_scores.size(); i++, rank++) {
    res.push_back(std::to_string(rank) + "." + " " + student_names[i] + ": " +
                  std::to_string(student_scores[i]));
  }

  return res;
}

// Create a string that contains the name of the first student to make a perfect
// score on the exam.
std::string perfect_score(std::vector<int> student_scores,
                          std::vector<std::string> student_names) {

  for (int i{0}; i < student_scores.size(); i++) {
    if (student_scores[i] == 100) {
      return student_names[i];
    }
  }

  return "";
}