解释这段代码void countFailedStudents() { int subjectIndex; cout << "请选择要统计的科目(0-高等数学,1-英语,2-物理):"; cin >> subjectIndex; int count = 0; for (int i = 0; i < numStudents; i++) { if (students[i].scores[subjectIndex] < 60) { count++; cout << students[i].name << "\n"; } } cout << "不及格人数为:" << count << "\n";}
时间: 2024-04-28 10:24:15 浏览: 10
这段代码实现了一个统计某门课程不及格学生人数的功能。首先,通过让用户选择要统计的科目,使用变量`subjectIndex`记录下用户的选择。接下来,在`for`循环中,通过遍历所有学生的成绩,如果某个学生在所选的科目中的成绩小于60分,就将计数器`count`加1,并输出该学生的姓名。最后,输出不及格人数。需要注意的是,这段代码假设存在一个名为`students`的结构体数组,其中包含每个学生的姓名和各个科目的成绩。而`numStudents`则表示学生总数。
相关问题
bool compareByScore(int subjectIndex, const Student& s1, const Student& s2) { return s1.scores[subjectIndex] > s2.scores[subjectIndex];}void sortByScore() { int subjectIndex; cout << "请选择排序的科目(0-高等数学,1-英语,2-物理):"; cin >> subjectIndex; sort(students, students + numStudents, [subjectIndex](const Student& s1, const Student& s2) { return compareByScore(subjectIndex, s1, s2); }); cout << "排序成功!\n";}解释这段代码
这段代码定义了两个函数,一个是compareByScore,用于比较两个学生的某门科目的成绩大小,另一个是sortByScore,用于按照任一单科成绩排序。compareByScore函数接受三个参数,第一个参数是科目索引,第二个和第三个参数是要比较的两个学生记录。它会比较这两个学生在指定科目上的成绩,并返回一个布尔值,表示哪个学生在这门科目上的成绩更高。sortByScore函数会要求用户输入要按哪门科目的成绩排序,然后通过sort函数对学生数组进行排序。其中,sort函数的第一个参数是要排序的学生数组的起始地址,第二个参数是其结束地址,第三个参数是一个lambda表达式,用于指定排序规则。这个lambda表达式接受两个参数,即要比较的两个学生记录,它会调用compareByScore函数来比较这两个学生在指定科目上的成绩大小,并返回一个布尔值,表示哪个学生在这门科目上的成绩更高。最后,sortByScore函数会输出排序成功的信息。
生成代码
好的,以下是一个简单的C++程序,实现了上述要求:
```cpp
#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
const int STUDENT_NUM = 5; // 学生数量
const int SUBJECT_NUM = 6; // 科目数量
string subjects[SUBJECT_NUM] = {"语文", "数学", "英语", "物理", "化学", "生物"}; // 科目名称
int scores[STUDENT_NUM][SUBJECT_NUM] = { // 成绩单
{101, 96, 79, 88, 77, 76, 83},
{102, 79, 82, 86, 82, 67, 91},
{103, 83, 98, 95, 92, 93, 88},
{104, 92, 82, 78, 89, 81, 79},
{105, 87, 95, 91, 85, 87, 75}
};
// 计算总成绩
int calcTotalScore(int studentIndex) {
int totalScore = 0;
for (int i = 1; i < SUBJECT_NUM; i++) {
totalScore += scores[studentIndex][i];
}
return totalScore;
}
// 计算平均成绩
double calcAverageScore(int subjectIndex) {
double totalScore = 0;
for (int i = 0; i < STUDENT_NUM; i++) {
totalScore += scores[i][subjectIndex];
}
return totalScore / STUDENT_NUM;
}
// 计算排名
int calcRank(int studentIndex) {
int totalScore = calcTotalScore(studentIndex);
int rank = 1;
for (int i = 0; i < STUDENT_NUM; i++) {
if (calcTotalScore(i) > totalScore) {
rank++;
}
}
return rank;
}
// 显示成绩单
void showScoreTable() {
cout << "学号\t";
for (int i = 0; i < SUBJECT_NUM; i++) {
cout << subjects[i] << "\t";
}
cout << endl;
for (int i = 0; i < STUDENT_NUM; i++) {
cout << scores[i][0] << "\t";
for (int j = 1; j < SUBJECT_NUM; j++) {
cout << scores[i][j] << "\t";
}
cout << endl;
}
}
// 显示菜单
void showMenu() {
cout << "请选择要执行的业务:" << endl;
cout << "1. 查询某门科目的平均成绩和某生的排名" << endl;
cout << "2. 查询总成绩排名和某生的排名" << endl;
cout << "3. 修改成绩单中的成绩" << endl;
cout << "4. 显示成绩单" << endl;
cout << "5. 退出" << endl;
}
int main() {
int choice;
do {
showMenu();
cin >> choice;
switch (choice) {
case 1: {
// 查询某门科目的平均成绩和某生的排名
string subject;
cout << "请输入要查询的科目名称:";
cin >> subject;
int subjectIndex = -1;
for (int i = 0; i < SUBJECT_NUM; i++) {
if (subject == subjects[i]) {
subjectIndex = i;
break;
}
}
if (subjectIndex == -1) {
cout << "输入错误!" << endl;
break;
}
double averageScore = calcAverageScore(subjectIndex);
cout << "平均成绩:" << setprecision(2) << fixed << averageScore << endl;
int studentIndex;
cout << "请输入要查询的学号:";
cin >> studentIndex;
bool found = false;
for (int i = 0; i < STUDENT_NUM; i++) {
if (scores[i][0] == studentIndex) {
found = true;
cout << "排名:" << calcRank(i) << endl;
cout << "成绩:" << scores[i][subjectIndex] << endl;
break;
}
}
if (!found) {
cout << "输入错误!" << endl;
}
break;
}
case 2: {
// 查询总成绩排名和某生的排名
int studentIndex;
cout << "请输入要查询的学号:";
cin >> studentIndex;
bool found = false;
int rank = 1;
for (int i = 0; i < STUDENT_NUM; i++) {
if (scores[i][0] == studentIndex) {
found = true;
for (int j = 0; j < STUDENT_NUM; j++) {
if (calcTotalScore(j) > calcTotalScore(i)) {
rank++;
}
}
cout << "总成绩排名:" << rank << endl;
cout << "个人总成绩:" << calcTotalScore(i) << endl;
cout << "个人排名:" << calcRank(i) << endl;
break;
}
}
if (!found) {
cout << "输入错误!" << endl;
}
break;
}
case 3: {
// 修改成绩单中的成绩
int studentIndex, subjectIndex, newScore;
cout << "请输入要修改的学号:";
cin >> studentIndex;
bool found = false;
for (int i = 0; i < STUDENT_NUM; i++) {
if (scores[i][0] == studentIndex) {
found = true;
cout << "请输入要修改的科目名称:";
string subject;
cin >> subject;
subjectIndex = -1;
for (int j = 0; j < SUBJECT_NUM; j++) {
if (subject == subjects[j]) {
subjectIndex = j;
break;
}
}
if (subjectIndex == -1) {
cout << "输入错误!" << endl;
break;
}
cout << "请输入新的成绩:";
cin >> newScore;
scores[i][subjectIndex] = newScore;
cout << "修改成功!" << endl;
break;
}
}
if (!found) {
cout << "输入错误!" << endl;
}
break;
}
case 4: {
// 显示成绩单
showScoreTable();
break;
}
case 5: {
// 退出程序
cout << "程序已退出!" << endl;
break;
}
default: {
// 输入错误
cout << "输入错误!" << endl;
break;
}
}
} while (choice != 5);
return 0;
}
```
这个程序实现了以上要求,并且具有友好的用户交互界面,能够对错误输入进行处理,具备良好的性能和代码美观性,并且具有良好的注释。