自動寄存櫃

#include <stdio.h>
#include <time.h>
#include <stdlib.h>

struct boxs{
    int id;
    int passwd;
    int is_used;
};

void init_boxs(struct boxs *, int);
int finding_available_boxes(struct boxs *, int);
int get_coin_num(void);
int create_rand_passwd(void);

int main(void){
    
 
struct boxs  c_box;
    int in_passwd, in_select, index, i, is_finded,BOX_NUM, is_over=0;

    srand((unsigned int)time(NULL));
    
    printf("暫存器總數:");
    scanf("%d", &BOX_NUM);
    struct boxs s_box[BOX_NUM];
    
    init_boxs(s_box, BOX_NUM);
    
    while (1) {
        if (is_over) {
            
 
break;
        }
        printf("1. 投硬幣  2.輸密碼  0.退出 請選擇: ");
        scanf("%d", &in_select);
        switch (in_select) {
            case 1:
                get_coin_num();
                index = finding_available_boxes(s_box, BOX_NUM);
                if (index != -1) {
//                    printf("index = %d", index);
 

                    c_box.passwd = create_rand_passwd();
                    c_box.is_used = 1;
                    s_box[index] = c_box;
                    printf("寄存箱編號: %d 密碼：%04d\n", index+1, c_box.passwd);
                }
                else{
                    printf("對不起，暫無可用空箱子!");
                }
                break;
            case 2:
                printf("請輸入密碼: ");
                scanf("%d", &in_passwd);
                is_finded = 0;
                for (i = 0; i < BOX_NUM; i++) {
                    if (s_box[i].is_used == 1 && s_box[i].passwd == in_passwd) {
                        printf("%d號箱已開啟\n", i+1);
                        s_box[i].is_used = 0;
                        is_finded = 1;
                        break;
                    }
                }
                if (!is_finded) {
                    printf("密碼錯誤.\n");
                }
                break;
            case 0:
                printf("結束\n");
                is_over = 1;
                break;
            }
    }
    
    return 0;
}

/* 初始化所有的箱子資料 */
void init_boxs(struct boxs *s_box, int BOX_NUM){
    int i;
    for (i = 0; i < BOX_NUM; i++) {
        (*s_box).id = i + 1;
        (*s_box).is_used = 0;
        s_box++;
    }
}

/* 查詢可用的空箱子 */
int finding_available_boxes(struct boxs *s_box, int BOX_NUM){
    int i, index = -1;
    for (i = 0; i < BOX_NUM; i++) {
        if ((*s_box).is_used == 0) {
            index = i;
            break;
        }
        s_box++;
    }
    return index;
}

/* 獲取投幣數 */
int get_coin_num(void){
    int r_num;
    while (1) {
        printf("投幣值: ");
        scanf("%d", &r_num);
        if (r_num == 1) {
            return r_num;
        }else{
            continue;
        }
    }
    return r_num;
}

/* 建立隨機密碼 */
int create_rand_passwd(void){
    int r_num = (rand()%10) * 1000 + (rand()%10) * 100 + (rand()%10) * 10 + rand()%10;
//    printf("%d\n", r_num);
    return r_num;
}