前言

在学生成绩管理系统中，必然面临着排序的问题。这里我们简单的将之前讲过的冒泡排序应用于我们的学生成绩管理系统中。
冒泡排序是一种简单的排序算法，它重复地遍历要排序的列表，比较相邻的两个项，如果相邻不是预期的顺序时交换它们，最终达到我们目标的顺序。

按照学生成绩高低进行排序

其核心在于排序算法: 将学生的分数进行比较，然后排序。

void swap(Student *a, Student *b)
{Student tmp = *a;*a = *b;*b = tmp;
}void bubble_sort_by_score(Student *s, int n)
{int i, j;for (i = 0; i < n-1; i++) {for (j = 0; j < n-i-1; j++) { // 最后 i 个已经排序好了, 遍历未排序的部分if (s[j].score < s[j+1].score) {// 如果当前元素大于后面的元素，交换它们swap(&s[j], &s[j+1]);}}}
}

完整代码如下:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h> // for access() function#define MAX_STUDENTS 100
#define MAX_NAME_LEN 50
#define STUDENT_SYSTEM "student_system"
#define TRUE 1
#define FALSE 0typedef struct {int id; // 学号char name[MAX_NAME_LEN]; // 姓名float score; // 成绩
} Student;int student_count = 0; // 学生数量Student *students; // 学生数组指针
int g_max_student = MAX_STUDENTS;Student *stu_sys_init(int num)
{Student *stu_sys;stu_sys = malloc(num * sizeof(Student));if (stu_sys == NULL) {printf("student system malloc failed!\n");}return stu_sys;
}int write_student_info(Student *s)
{FILE *fp = fopen(STUDENT_SYSTEM, "a");if (fp == NULL) {printf("fopen student_system failed!\n");return 1;}fprintf(fp, "%-4d %-10s %-.2f\n", s->id, s->name, s->score);fclose(fp);return 0;
}int check_if_student_exsit(int id)
{int i;for(i = 0; i < student_count; i++) {if(students[i].id == id) {return 1;}}return 0;
}void update_student_info(Student s, int need_write)
{Student *stu_reinit;int old_max_student;int i;if(student_count >= g_max_student) {old_max_student = g_max_student;g_max_student = g_max_student << 1;stu_reinit = stu_sys_init(g_max_student);if (stu_reinit == NULL) {printf("Database is full!\n");return;}memcpy(stu_reinit, students, old_max_student * sizeof(Student));free(students);students = stu_reinit;}if (!check_if_student_exsit(s.id)) {students[student_count++] = s;if (need_write) {printf("Student added successfully, all student: %d!\n", student_count);write_student_info(&s);}} else {printf("student has in db, do nothing!\n");}
}void add_student()
{Student s;printf("Enter student ID: ");scanf("%d", &s.id);printf("Enter student name: ");scanf("%s", s.name);s.score = 0.0; // 初始成绩设置为0update_student_info(s, TRUE);
}void print_title()
{printf("%-4s %-10s %-5s\n", "ID", "Name", "Score");
}void display_all_students()
{int i;printf("-------- All students info --------\n");if (student_count == 0) {printf("No students!\n");} else {print_title();for(i = 0; i < student_count; i++) {printf("%-4d %-10s %-.2f\n", students[i].id, students[i].name, students[i].score);}}printf("--------      End       -----------\n");
}void find_student_by_id()
{int id, i;printf("Enter student ID to search: ");scanf("%d", &id);for(i = 0; i < student_count; i++) {if(students[i].id == id) {print_title();printf("%-4d %-10s %-.2f\n", students[i].id, students[i].name, students[i].score);return;}}printf("Student with ID %d not found!\n", id);
}void find_student_by_name()
{int i, is_find = 0;char name[MAX_NAME_LEN];printf("Enter student name to search: ");scanf("%s", name);for(i = 0; i < student_count; i++) {if(strcmp(students[i].name, name) == 0) {print_title();printf("%-4d %-10s %-.2f\n", students[i].id, students[i].name, students[i].score);is_find = 1;}}if (is_find == 0) {printf("Student with name %s not found!\n", name);}
}void add_score()
{int id, i;float score;printf("Enter student ID: ");scanf("%d", &id);printf("Enter student score: ");scanf("%f", &score);for(i = 0; i < student_count; i++) {if(students[i].id == id) {students[i].score = score;printf("Score added successfully!\n");return;}}printf("Student with ID %d not found!\n", id);
}void display_average_score()
{float total = 0.0;int i;for(i = 0; i < student_count; i++) {total += students[i].score;}printf("Average score of all students: %.2f\n", total / student_count);
}int init_student_info()
{if(access(STUDENT_SYSTEM, F_OK) != 0) { // 文件不存在return 0;}FILE *fp = fopen(STUDENT_SYSTEM, "r");if (fp == NULL) {printf("fopen student_system failed!\n");return 1;}#define BUF_SIZE 1024char buf[BUF_SIZE];int i = 0;Student s;while(fgets(buf, BUF_SIZE - 1, fp) != NULL) {sscanf(buf, "%d %s %f\n", &s.id, s.name, &s.score);update_student_info(s, FALSE);}fclose(fp);return 0;}void swap(Student *a, Student *b)
{Student tmp = *a;*a = *b;*b = tmp;
}void bubble_sort_by_score(Student *s, int n)
{int i, j;for (i = 0; i < n-1; i++) {for (j = 0; j < n-i-1; j++) { // 最后 i 个已经排序好了, 遍历未排序的部分if (s[j].score < s[j+1].score) {// 如果当前元素大于后面的元素，交换它们swap(&s[j], &s[j+1]);}}}
}int main()
{int choice;int ret;students = stu_sys_init(MAX_STUDENTS);if (students == NULL) {printf("student system init failed, exit!\n");return -1;}ret = init_student_info();if (ret) {printf("init_student_info failed!\n");return 1;}display_all_students();do {printf("\nStudent Score Management System\n");printf("0. Exit\n");printf("1. Add Student\n");printf("2. Display All Students\n");printf("3. Find Student by ID\n");printf("4. Find Student by Name\n");printf("5. Add Score\n");printf("6. Display Average Score\n");printf("7. Display by Score sort\n");printf("Enter your choice: ");scanf("%d", &choice);switch(choice) {case 0:printf("Exiting...\n");break;case 1:add_student();break;case 2:display_all_students();break;case 3:find_student_by_id();break;case 4:find_student_by_name();break;case 5:add_score();break;case 6:display_average_score();break;case 7:bubble_sort_by_score(students, student_count);display_all_students();break;default:printf("Invalid choice!\n");}} while(choice != 0);return 0;
}