已知有20个学生记录（包括学号，姓名，成绩） 设计三个查找算法，分别实现按学号，姓名，菜单选择查找方式；c语言

以下是按学号查找的示例代码：

#include <stdio.h>
#define N 20

struct student {
    int id;
    char name[20];
    int score;
};

int search_by_id(struct student list[], int n, int target) {
    // 二分查找
    int left = 0, right = n-1;
    while (left <= right) {
        int mid = (left + right) / 2;
        if (list[mid].id == target) {
            return mid;
        } else if (list[mid].id < target) {
            left = mid + 1;
        } else {
            right = mid - 1;
        }
    }
    return -1;
}

int main() {
    struct student list[N] = {{1, "Alice", 80}, {3, "Bob", 90}, {5, "Charlie", 85}, {7, "David", 95}, {9, "Emily", 70},
                              {11, "Frank", 75}, {13, "Grace", 95}, {15, "Henry", 60}, {17, "Ivy", 85}, {19, "Jason", 90},
                              {2, "Kevin", 85}, {4, "Lucy", 90}, {6, "Maggie", 80}, {8, "Nancy", 70}, {10, "Oscar", 65},
                              {12, "Peggy", 95}, {14, "Queenie", 85}, {16, "Roger", 80}, {18, "Steven", 60}, {20, "Tom", 70}};
    int target_id;
    printf("请输入要查找的学号：");
    scanf("%d", &target_id);
    int index = search_by_id(list, N, target_id);
    if (index != -1) {
        printf("学号：%d，姓名：%s，成绩：%d\n", list[index].id, list[index].name, list[index].score);
    } else {
        printf("未找到该学生信息！\n");
    }
    return 0;
}

以下是按姓名查找的示例代码：

#include <stdio.h>
#include <string.h>
#define N 20

struct student {
    int id;
    char name[20];
    int score;
};

int search_by_name(struct student list[], int n, char target[]) {
    // 线性查找
    for (int i = 0; i < n; i++) {
        if (strcmp(list[i].name, target) == 0) {
            return i;
        }
    }
    return -1;
}

int main() {
    struct student list[N] = {{1, "Alice", 80}, {3, "Bob", 90}, {5, "Charlie", 85}, {7, "David", 95}, {9, "Emily", 70},
                              {11, "Frank", 75}, {13, "Grace", 95}, {15, "Henry", 60}, {17, "Ivy", 85}, {19, "Jason", 90},
                              {2, "Kevin", 85}, {4, "Lucy", 90}, {6, "Maggie", 80}, {8, "Nancy", 70}, {10, "Oscar", 65},
                              {12, "Peggy", 95}, {14, "Queenie", 85}, {16, "Roger", 80}, {18, "Steven", 60}, {20, "Tom", 70}};
    char target_name[20];
    printf("请输入要查找的姓名：");
    scanf("%s", target_name);
    int index = search_by_name(list, N, target_name);
    if (index != -1) {
        printf("学号：%d，姓名：%s，成绩：%d\n", list[index].id, list[index].name, list[index].score);
    } else {
        printf("未找到该学生信息！\n");
    }
    return 0;
}

以下是菜单选择查找方式的示例代码：

#include <stdio.h>
#include <string.h>
#define N 20

struct student {
    int id;
    char name[20];
    int score;
};

int search_by_id(struct student list[], int n, int target) {
    // 二分查找
    int left = 0, right = n-1;
    while (left <= right) {
        int mid = (left + right) / 2;
        if (list[mid].id == target) {
            return mid;
        } else if (list[mid].id < target) {
            left = mid + 1;
        } else {
            right = mid - 1;
        }
    }
    return -1;
}

int search_by_name(struct student list[], int n, char target[]) {
    // 线性查找
    for (int i = 0; i < n; i++) {
        if (strcmp(list[i].name, target) == 0) {
            return i;
        }
    }
    return -1;
}

int main() {
    struct student list[N] = {{1, "Alice", 80}, {3, "Bob", 90}, {5, "Charlie", 85}, {7, "David", 95}, {9, "Emily", 70},
                              {11, "Frank", 75}, {13, "Grace", 95}, {15, "Henry", 60}, {17, "Ivy", 85}, {19, "Jason", 90},
                              {2, "Kevin", 85}, {4, "Lucy", 90}, {6, "Maggie", 80}, {8, "Nancy", 70}, {10, "Oscar", 65},
                              {12, "Peggy", 95}, {14, "Queenie", 85}, {16, "Roger", 80}, {18, "Steven", 60}, {20, "Tom", 70}};
    int choice, target_id;
    char target_name[20];
    printf("请选择查找方式（1为按学号查找，2为按姓名查找）：");
    scanf("%d", &choice);
    switch (choice) {
        case 1:
            printf("请输入要查找的学号：");
            scanf("%d", &target_id);
            int index = search_by_id(list, N, target_id);
            if (index != -1) {
                printf("学号：%d，姓名：%s，成绩：%d\n", list[index].id, list[index].name, list[index].score);
            } else {
                printf("未找到该学生信息！\n");
            }
            break;
        case 2:
            printf("请输入要查找的姓名：");
            scanf("%s", target_name);
            int index2 = search_by_name(list, N, target_name);
            if (index2 != -1) {
                printf("学号：%d，姓名：%s，成绩：%d\n", list[index2].id, list[index2].name, list[index2].score);
            } else {
                printf("未找到该学生信息！\n");
            }
            break;
        default:
            printf("输入有误！\n");
            break;
    }
    return 0;
}