C12节：练习和作业

1 贪吃蛇练习

/*
    贪吃蛇练习
*/
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define     SIZE             4
enum {UP, DOWN, LEFT, RIGHT};
typedef struct {
    int x;
    int y;
} position;
void show_snake(position *p_position, int size) {
    int pos = 0;
    for (pos = 0;pos <= size - 1;pos++) {
        printf("(%d,%d) ", p_position[pos].x, p_position[pos].y);
    }
    printf("\n");
}
int main() {
    int pos = 0, direction = 0;
    position snake[SIZE], head;
    srand(time(0));
    snake[0].x = rand() % 10;
    snake[0].y = rand() % 10;
    for (pos = 1;pos <= SIZE - 1;pos++) {
        snake[pos] = snake[pos - 1];
        snake[pos].x++;
    }
    show_snake(snake, SIZE);
    while (1) {
        printf("请输入方向（%d代表上，%d代表下，%d代表左，%d代表右）：", UP, DOWN, LEFT, RIGHT);
        scanf("%d", &direction);
        head = snake[0];
        switch(direction) {
        case UP:
            head.y--;
            break;
        case DOWN:
            head.y++;
            break;
        case LEFT:
            head.x--;
            break;
        case RIGHT:
            head.x++;
            break;
        }
        for (pos = 0;pos <= SIZE - 1;pos++) {
            if (head.x == snake[pos].x &&
                head.y == snake[pos].y) {
                break;
            }
        }
        if (pos <= SIZE - 1) {
            printf("方向错误\n");
        }
        else {
            for (pos = SIZE - 2;pos >= 0;pos--) {
                snake[pos + 1] = snake[pos];
            }
            snake[0] = head;
            show_snake(snake, SIZE);
        }
    }
    return 0;
}

2   --1.从键盘得到日程信息并最终输出。
       每个日程包含小时数（0--23）和内容两部分
       不要求排序
    --2.对结果进行排序

/*
    结构体练习
*/
#include <stdio.h>
#include <string.h>
struct month {
    char name[10];
    int days;
};
int main() {
    struct month months[12];
    char * names[] =   {"Jan", "Feb", "Mar",
                        "Apr", "May", "Jun",
                        "Jul", "Aug", "Sep",
                        "Oct", "Nov", "Dec"};
    int days[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    int loop = 0;
    for (loop = 0;loop <= 11;loop++) {
        strcpy(months[loop].name, names[loop]);
        months[loop].days = days[loop];
    }
    for (loop = 0;loop <= 11;loop++) {
        printf("名称是%s,天数是%d\n", months[loop].name, months[loop].days);
    }
    return 0;
}

/*
    结构体初始化练习
*/
#include <stdio.h>
/*struct month {
    char name[10];
    int days;
};
typedef struct month month;*/
typedef struct /*month*/ {
    char name[10];
    int days;
} month;
int main() {
    month months[3] = {{"Jan", 31},
                              {"Feb", 28},
                              {"Mar", 31}};
    int loop = 0;
    for (loop = 0;loop <= 2;loop++) {
        printf("名称是%s,天数是%d\n", months[loop].name, months[loop].days);
    }
    return 0;
}

3 编写一个函数录入多个人员信息。每次录入之前都向用户询问。

/*
    人员信息管理系统练习
*/
#include <stdio.h>
#include <string.h>
int save() {
    int num = 0, ids[10] = {}, id = 0, pos = 0;
    char name[20] = {}, buf[20] = {};
    float salary = 0.0f;
    FILE *p_file = fopen("a.bin", "ab");
    if (!p_file) {
        printf("文件打开失败\n");
        return 0;
    }
    while (1) {
        printf("请输入人员id：");
        scanf("%d", &id);
        scanf("%*[^\n]");
        scanf("%*c");
        for (pos = 0;pos <= num - 1;pos++) {
            if (id == ids[pos]) {
                break;
            }
        }
        if (pos <= num - 1) {
            continue;
        }
        printf("请输入人员姓名：");
        fgets(name, 20, stdin);
        if (strlen(name) == 19 && name[18] != '\n') {
            scanf("%*[^\n]");
            scanf("%*c");
        }
        printf("请输入人员工资：");
        scanf("%g", &salary);
        scanf("%*[^\n]");
        scanf("%*c");
        fwrite(&id, sizeof(int), 1, p_file);
        fwrite(name, sizeof(char), 20, p_file);
        fwrite(&salary, sizeof(float), 1, p_file);
        ids[num] = id;
        num++;
        printf("是否要录入下一个员工信息：");
        fgets(buf, 20, stdin);
        if (strlen(buf) == 19 && buf[18] != '\n') {
            scanf("%*[^\n]");
            scanf("%*c");
        }
        if (buf[0] != 'y' && buf[0] != 'Y') {
            break;
        }
    }
    fclose(p_file);
    return num;
}
int main() {
    printf("共录入了%d个用户的信息\n", save());
    return 0;
}

4 编写函数完成基于id的查询功能

/*
    id比较练习
*/
#include <stdio.h>
int main() {
    int id = 0, id1 = 0, length = 0;
    FILE *p_file = NULL;
    printf("请输入一个id：");
    scanf("%d", &id);
    p_file = fopen("a.bin", "rb");
    if (p_file) {
        fseek(p_file, 0, SEEK_END);
        length = ftell(p_file);
        rewind(p_file);
        while(ftell(p_file) < length) {
            fread(&id1, sizeof(int), 1, p_file);
            if (id == id1) {
                printf("id已存在\n");
                break;
            }
            fseek(p_file, 24, SEEK_CUR);
        }
        if (ftell(p_file) >= length) {
            printf("id不存在\n");
        }
        fclose(p_file);
        p_file = NULL;
    }
    return 0;
}