# SIMS-LITE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_STUDENTS 100

typedef struct {
    char id[20];    // 学号
    char name[50];  // 姓名
    float score;    // 成绩
} Student;

typedef struct {
    Student students[MAX_STUDENTS];
    int length;     // 当前学生数量
} StudentList;

// 初始化学生列表
void InitList(StudentList *L) {
    L->length = 0;
}

// (1) 逐个输入学生信息
void InputStudents(StudentList *L) {
    int n;
    printf("请输入学生人数(不超过%d): ", MAX_STUDENTS);
    scanf("%d", &n);
    
    if (n <= 0 || n > MAX_STUDENTS) {
        printf("输入人数不合法!\n");
        return;
    }
    
    for (int i = 0; i < n; i++) {
        printf("请输入第%d个学生的信息:\n", i+1);
        printf("学号: ");
        scanf("%s", L->students[L->length].id);
        printf("姓名: ");
        scanf("%s", L->students[L->length].name);
        printf("成绩: ");
        scanf("%f", &L->students[L->length].score);
        L->length++;
    }
    printf("输入完成!\n");
}

// (2) 显示所有学生信息
void DisplayStudents(StudentList *L) {
    if (L->length == 0) {
        printf("没有学生信息!\n");
        return;
    }
    
    printf("学号\t姓名\t成绩\n");
    printf("----------------------------\n");
    for (int i = 0; i < L->length; i++) {
        printf("%s\t%s\t%.1f\n", 
               L->students[i].id, 
               L->students[i].name, 
               L->students[i].score);
    }
}

// (3) 在指定位置插入学生信息
void InsertStudent(StudentList *L) {
    if (L->length >= MAX_STUDENTS) {
        printf("学生列表已满，无法插入!\n");
        return;
    }
    
    int pos;
    printf("请输入要插入的位置(1-%d): ", L->length + 1);
    scanf("%d", &pos);
    
    if (pos < 1 || pos > L->length + 1) {
        printf("位置不合法!\n");
        return;
    }
    
    Student s;
    printf("请输入学生信息:\n");
    printf("学号: ");
    scanf("%s", s.id);
    printf("姓名: ");
    scanf("%s", s.name);
    printf("成绩: ");
    scanf("%f", &s.score);
    
    // 将pos-1之后的元素后移
    for (int i = L->length; i >= pos; i--) {
        L->students[i] = L->students[i-1];
    }
    
    L->students[pos-1] = s;
    L->length++;
    printf("插入成功!\n");
}

// (4) 删除指定位置的学生记录
void DeleteStudent(StudentList *L) {
    if (L->length == 0) {
        printf("学生列表为空，无法删除!\n");
        return;
    }
    
    int pos;
    printf("请输入要删除的位置(1-%d): ", L->length);
    scanf("%d", &pos);
    
    if (pos < 1 || pos > L->length) {
        printf("位置不合法!\n");
        return;
    }
    
    printf("删除的学生信息: %s %s %.1f\n", 
           L->students[pos-1].id, 
           L->students[pos-1].name, 
           L->students[pos-1].score);
    
    // 将pos之后的元素前移
    for (int i = pos; i < L->length; i++) {
        L->students[i-1] = L->students[i];
    }
    
    L->length--;
    printf("删除成功!\n");
}

// (5) 统计学生个数
void CountStudents(StudentList *L) {
    printf("当前学生人数: %d\n", L->length);
}

// 直接插入排序 - 按姓名
void InsertionSortByName(StudentList *L) {
    int i, j;
    Student temp;
    
    for (i = 1; i < L->length; i++) {
        temp = L->students[i];
        j = i - 1;
        
        while (j >= 0 && strcmp(L->students[j].name, temp.name) > 0) {
            L->students[j+1] = L->students[j];
            j--;
        }
        
        L->students[j+1] = temp;
    }
    printf("按姓名排序完成!\n");
}

// 快速排序分区函数 - 按学号
int Partition(StudentList *L, int low, int high) {
    Student pivot = L->students[low];
    
    while (low < high) {
        while (low < high && strcmp(L->students[high].id, pivot.id) >= 0) {
            high--;
        }
        L->students[low] = L->students[high];
        
        while (low < high && strcmp(L->students[low].id, pivot.id) <= 0) {
            low++;
        }
        L->students[high] = L->students[low];
    }
    
    L->students[low] = pivot;
    return low;
}

// 快速排序递归函数 - 按学号
void QuickSort(StudentList *L, int low, int high) {
    if (low < high) {
        int pivotpos = Partition(L, low, high);
        QuickSort(L, low, pivotpos - 1);
        QuickSort(L, pivotpos + 1, high);
    }
}

// (6) 排序功能
void SortStudents(StudentList *L) {
    if (L->length == 0) {
        printf("没有学生信息，无法排序!\n");
        return;
    }
    
    int choice;
    printf("请选择排序方式:\n");
    printf("1. 按姓名排序(直接插入排序)\n");
    printf("2. 按学号排序(快速排序)\n");
    printf("请选择: ");
    scanf("%d", &choice);
    
    switch (choice) {
        case 1:
            InsertionSortByName(L);
            break;
        case 2:
            QuickSort(L, 0, L->length - 1);
            printf("按学号排序完成!\n");
            break;
        default:
            printf("无效选择!\n");
    }
}

// (7) 折半查找 - 按学号
void BinarySearchById(StudentList *L) {
    if (L->length == 0) {
        printf("没有学生信息，无法查找!\n");
        return;
    }
    
    // 先确保按学号有序
    QuickSort(L, 0, L->length - 1);
    
    char targetId[20];
    printf("请输入要查找的学号: ");
    scanf("%s", targetId);
    
    int low = 0, high = L->length - 1, mid;
    while (low <= high) {
        mid = (low + high) / 2;
        
        int cmp = strcmp(L->students[mid].id, targetId);
        if (cmp == 0) {
            printf("查找成功!\n");
            printf("学号: %s, 姓名: %s, 成绩: %.1f\n", 
                   L->students[mid].id, 
                   L->students[mid].name, 
                   L->students[mid].score);
            return;
        } else if (cmp < 0) {
            low = mid + 1;
        } else {
            high = mid - 1;
        }
    }
    
    printf("未找到学号为 %s 的学生!\n", targetId);
}

// 显示菜单
void ShowMenu() {
    printf("\n简易学生信息管理系统\n");
    printf("1. 输入学生信息\n");
    printf("2. 显示所有学生信息\n");
    printf("3. 插入学生信息\n");
    printf("4. 删除学生信息\n");
    printf("5. 统计学生人数\n");
    printf("6. 排序学生信息\n");
    printf("7. 查找学生信息\n");
    printf("0. 退出系统\n");
    printf("请选择操作: ");
}

int main() {
    StudentList list;
    InitList(&list);
    
    int choice;
    do {
        ShowMenu();
        scanf("%d", &choice);
        
        switch (choice) {
            case 1:
                InputStudents(&list);
                break;
            case 2:
                DisplayStudents(&list);
                break;
            case 3:
                InsertStudent(&list);
                break;
            case 4:
                DeleteStudent(&list);
                break;
            case 5:
                CountStudents(&list);
                break;
            case 6:
                SortStudents(&list);
                break;
            case 7:
                BinarySearchById(&list);
                break;
            case 0:
                printf("感谢使用，再见!\n");
                break;
            default:
                printf("无效选择，请重新输入!\n");
        }
    } while (choice != 0);
    
    return 0;
}