分析一下这段代码 switch (choice) { case 1: printf("请输入人数(最大为%d):", MAX_N); scanf("%d", &n); if (n > MAX_N) { printf("人数超过最大限制!\n"); break; } people = (Person*)malloc(n * sizeof(Person)); flag = (int*)calloc(n, sizeof(int)); // 初始时所有人都未被丢下去
时间: 2024-02-14 16:32:38 浏览: 19
这段代码中使用了 switch-case 语句来根据变量 choice 的值进行不同的操作。其中,当 choice 的值为 1 时,会先提示用户输入人数 n,并进行一定的判断。如果输入的人数超过了最大限制 MAX_N,则会输出提示信息并跳出 switch-case 语句。否则,会使用 malloc 函数动态分配 n 个 Person 类型的内存空间,并使用 calloc 函数初始化一个大小为 n 的 int 类型数组 flag,用于标记每个人是否已经被“丢下去”了。这段代码的作用是为了初始化一些变量,为后面的程序逻辑做准备。
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修改代码错误int main() { int i,choice,score;// 交互式查询 char query[20]; int num_students = read_student_info(students); printf("学生成绩表:\n"); display_all_students(students, num_students); while (1) { printf("\t\t\t\t\t-------- 学生成绩管理系统-------\n\n\n\n"); //菜单 printf("\t\t\t\t\t1. 增加学生记录\n\n"); printf("\t\t\t\t\t2. 查询学生记录\n\n"); printf("\t\t\t\t\t3. 查询学生记录\n\n"); printf("\t\t\t\t\t4. 按平均成绩排序\n\n"); printf("\t\t\t\t\t4. 退出\n\n\n"); printf("请选择(0-4):"); scanf("%d", &i); if (i == 4) { break; } else switch (i) { case 1:addStudent();break; case 2:printf("请输入排序类型:\n"); printf("1. 按学号递增排序\n"); printf("2. 按总分递减查询\n"); scanf("%d", &choice); switch (choice){ case 1:sort_by_num();break; case 2:sort_by_score();break; default: printf("无效的输入!\n"); } case 3: printf("请输入查询类型:\n"); printf("1. 按学号查询\n"); printf("2. 按姓名查询\n"); printf("3. 按总分查询\n"); scanf("%d", &choice); switch (choice){ printf("请输入学号:"); scanf("%s", query); search_by_num(query);break; case 2: printf("请输入姓名:"); scanf("%s", query); search_by_name(query); break; case 3: printf("请输入分数:"); scanf("%d", &score); search_by_score(score);break; default: printf("无效的输入!\n"); } } } return 0; }
在您提供的代码中,有几个错误需要注意:
1. 在 `int num_students = read_student_info(students);` 语句中,变量 `students` 没有被声明或定义。您需要在此之前声明一个 `student` 类型的数组,并将其传递给 `read_student_info` 函数。
2. 在 `case 3:` 中的 `switch` 语句中,`case` 语句缺少了一个左括号。
3. 在 `case 3:` 中的 `switch` 语句中,`case 1:` 和 `case 2:` 中的代码缺少了一个 `break` 语句。这可能会导致程序在执行完一个 `case` 后继续执行下一个 `case`。
4. 在 `case 3:` 中的 `switch` 语句中,`case 1:` 和 `case 2:` 的代码块中缺少了一个右括号。
5. 在 `case 3:` 中的 `switch` 语句中,`case 3:` 中的代码块中的函数名 `search_by_score` 没有被定义或声明。您需要确保在使用该函数之前已经声明或定义了它。
下面是修改过的代码:
```
int main() {
int i, choice, score; // 交互式查询
char query[20];
student students[MAX_STUDENTS]; // 声明一个 student 类型的数组
int num_students = read_student_info(students);
printf("学生成绩表:\n");
display_all_students(students, num_students);
while (1) {
printf("\t\t\t\t\t-------- 学生成绩管理系统-------\n\n\n\n"); //菜单
printf("\t\t\t\t\t1. 增加学生记录\n\n");
printf("\t\t\t\t\t2. 查询学生记录\n\n");
printf("\t\t\t\t\t3. 查询学生成绩\n\n");
printf("\t\t\t\t\t4. 按平均成绩排序\n\n");
printf("\t\t\t\t\t5. 退出\n\n\n");
printf("请选择(0-4):");
scanf("%d", &i);
if (i == 5) {
break;
} else {
switch (i) {
case 1:
addStudent();
break;
case 2:
printf("请输入排序类型:\n");
printf("1. 按学号递增排序\n");
printf("2. 按总分递减查询\n");
scanf("%d", &choice);
switch (choice){
case 1:
sort_by_num();
break;
case 2:
sort_by_score();
break;
default:
printf("无效的输入!\n");
break; // 添加 break 语句
}
break;
case 3:
printf("请输入查询类型:\n");
printf("1. 按学号查询\n");
printf("2. 按姓名查询\n");
printf("3. 按总分查询\n");
scanf("%d", &choice);
switch (choice){
case 1:
printf("请输入学号:");
scanf("%s", query);
search_by_num(query);
break;
case 2:
printf("请输入姓名:");
scanf("%s", query);
search_by_name(query);
break;
case 3:
printf("请输入分数:");
scanf("%d", &score);
search_by_score(students, num_students, score); // 添加参数
break;
default:
printf("无效的输入!\n");
break; // 添加 break 语句
}
break;
default:
printf("无效的输入!\n");
break; // 添加 break 语句
}
}
}
return 0;
}
```
用c语言给这段代码加入删除学生信息和修改学生信息的功能,要求这段代码可在dev c++上可以运行。并对这段代码的功能进行介绍#include <stdio.h>#include <stdlib.h>#include <string.h>#define MAX_STUDENTS 20#define NAME_LENGTH 20typedef struct { char name[NAME_LENGTH]; int age; float grade;} Student;void add_student(Student *students, int *num_students);void search_student(Student *students, int num_students);void display_students(Student *students, int num_students);int main() { Student students[MAX_STUDENTS]; int num_students = 0; int choice; do { printf("\n1. Add student\n2. Search student\n3. Display all students\n4. Exit\n"); printf("Enter your choice: "); scanf("%d", &choice); switch (choice) { case 1: add_student(students, &num_students); break; case 2: search_student(students, num_students); break; case 3: display_students(students, num_students); break; case 4: printf("Exiting program...\n"); break; default: printf("Invalid choice.\n"); } } while (choice != 4); return 0;}void add_student(Student *students, int *num_students) { if (*num_students >= MAX_STUDENTS) { printf("Maximum number of students reached.\n"); return; } Student *new_student = &students[*num_students]; printf("Enter name: "); scanf("%s", new_student->name); printf("Enter age: "); scanf("%d", &new_student->age); printf("Enter grade: "); scanf("%f", &new_student->grade); *num_students += 1; printf("Student added.\n");}void search_student(Student *students, int num_students) { char name[NAME_LENGTH]; printf("Enter name to search: "); scanf("%s", name); for (int i = 0; i < num_students; i++) { if (strcmp(students[i].name, name) == 0) { printf("Name: %s\nAge: %d\nGrade: %0.2f\n", students[i].name, students[i].age, students[i].grade); return; } } printf("Student not found.\n");}void display_students(Student *students, int num_students) { for (int i = 0; i < num_students; i++) { printf("Name: %s\nAge: %d\nGrade: %0.2f\n", students[i].name, students[i].age, students[i].grade); printf("---------------------\n"); }}
好的,我会为您解答这个问题。首先,我需要说明的是,为了加入删除和修改学生信息的功能,我们需要对原有的代码进行一定的修改和增加。下面是修改后的代码:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_STUDENTS 20
#define NAME_LENGTH 20
typedef struct {
char name[NAME_LENGTH];
int age;
float grade;
} Student;
void add_student(Student *students, int *num_students);
void search_student(Student *students, int num_students);
void display_students(Student *students, int num_students);
void delete_student(Student *students, int *num_students);
void modify_student(Student *students, int num_students);
int main() {
Student students[MAX_STUDENTS];
int num_students = 0;
int choice;
do {
printf("\n1. Add student\n2. Search student\n3. Display all students\n4. Delete student\n5. Modify student\n6. Exit\n");
printf("Enter your choice: ");
scanf("%d", &choice);
switch (choice) {
case 1:
add_student(students, &num_students);
break;
case 2:
search_student(students, num_students);
break;
case 3:
display_students(students, num_students);
break;
case 4:
delete_student(students, &num_students);
break;
case 5:
modify_student(students, num_students);
break;
case 6:
printf("Exiting program...\n");
break;
default:
printf("Invalid choice.\n");
}
} while (choice != 6);
return 0;
}
void add_student(Student *students, int *num_students) {
if (*num_students >= MAX_STUDENTS) {
printf("Maximum number of students reached.\n");
return;
}
Student *new_student = &students[*num_students];
printf("Enter name: ");
scanf("%s", new_student->name);
printf("Enter age: ");
scanf("%d", &new_student->age);
printf("Enter grade: ");
scanf("%f", &new_student->grade);
*num_students += 1;
printf("Student added.\n");
}
void search_student(Student *students, int num_students) {
char name[NAME_LENGTH];
printf("Enter name to search: ");
scanf("%s", name);
for (int i = 0; i < num_students; i++) {
if (strcmp(students[i].name, name) == 0) {
printf("Name: %s\nAge: %d\nGrade: %0.2f\n", students[i].name, students[i].age, students[i].grade);
return;
}
}
printf("Student not found.\n");
}
void display_students(Student *students, int num_students) {
for (int i = 0; i < num_students; i++) {
printf("Name: %s\nAge: %d\nGrade: %0.2f\n", students[i].name, students[i].age, students[i].grade);
printf("---------------------\n");
}
}
void delete_student(Student *students, int *num_students) {
char name[NAME_LENGTH];
printf("Enter name to delete: ");
scanf("%s", name);
for (int i = 0; i < *num_students; i++) {
if (strcmp(students[i].name, name) == 0) {
for (int j = i; j < *num_students - 1; j++) {
students[j] = students[j + 1];
}
*num_students -= 1;
printf("Student %s deleted.\n", name);
return;
}
}
printf("Student not found.\n");
}
void modify_student(Student *students, int num_students) {
char name[NAME_LENGTH];
printf("Enter name to modify: ");
scanf("%s", name);
for (int i = 0; i < num_students; i++) {
if (strcmp(students[i].name, name) == 0) {
printf("Enter new name: ");
scanf("%s", students[i].name);
printf("Enter new age: ");
scanf("%d", &students[i].age);
printf("Enter new grade: ");
scanf("%f", &students[i].grade);
printf("Student %s modified.\n", name);
return;
}
}
printf("Student not found.\n");
}
```
这段代码的修改主要是在 `main()` 函数中增加了两个选项:删除学生信息和修改学生信息。同时,我们还需要添加两个新的函数 `delete_student()` 和 `modify_student()`。
其中, `delete_student()` 函数用于删除学生信息。我们需要输入要删除的学生姓名,然后遍历学生数组,找到要删除的学生后将其从数组中删除,最后将学生数量减一。
`modify_student()` 函数用于修改学生信息。同样地,我们需要输入要修改的学生姓名,然后遍历学生数组,找到要修改的学生后分别输入新的姓名、年龄和成绩,最后打印修改成功的信息。
我希望这个修改后的代码可以满足您的需求,如果您有任何问题或疑惑,请随时向我提问。
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