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#include <stdio.h>

typedef struct { int *pt; int co; } DsSo;

/* Xoa mot phan tu khoi danh sach */
int remove(DsSo *d, int vi_tri) {
    if (vi_tri < 0 || vi_tri >= d->co) return -1;
    for (int i = vi_tri; i + 1 < d->co; ++i) d->pt[i] = d->pt[i + 1];
    d->co--;
    return 0;
}

int dem_ky_tu(const char *s) {
    int n = 0;
    while (*s) { if (*s != ' ') ++n; ++s; }   /* KHONG dem dau cach */
    return n;
}

/* Ten noi "dem ky tu", ma khong dem dau cach.
   Nguoi goi tin ten, khong doc than ham, va sinh ra mot loi.

   Ten dung: dem_ky_tu_khong_trang, hoac doi ham cho khop ten. */

typedef struct { ... } NguoiDung;

NguoiDung *lay_nguoi_dung(int id);
NguoiDung *tim_user(const char *ten);
NguoiDung *doc_tai_khoan(int id);
NguoiDung *nap_thanh_vien(int id);

/* Bon tu cho MOT khai niem, va ba dong tu cho MOT hanh dong.
   Nguoi doc phai tu hoi: "doc" va "nap" khac nhau cho nao?

   Chon MOT tu cho MOI khai niem va viet vao tai lieu:
     nguoi_dung   khong dung user, tai khoan, thanh vien
     lay          khong dung tim, doc, nap  */

NguoiDung *nguoi_dung_lay_theo_id(int id);
NguoiDung *nguoi_dung_lay_theo_ten(const char *ten);

int  xu_ly_don_hang(Don *d);
int  xu_ly_don_hang_2(Don *d);
int  xu_ly_don_hang_moi(Don *d);
int  xu_ly_don_hang_cu(Don *d);

/* Ban se goi nham. Khong phai co the, ma la chac chan.
   Nhat la trong danh sach tu dong hoan thanh cua trinh soan thao.

   Neu ban thay minh dat ten kieu nay, do la dau hieu thiet ke sai:
   bon ham do co gi khac nhau ma khong noi ra duoc bang tu? */

int don_hang_xac_nhan(Don *d);
int don_hang_huy(Don *d);
int don_hang_giao(Don *d);

int    iSoLuong;            /* ky phap Hungary */
char  *szTen;
double dGiaTri;
LPCSTR lpszDuongDan;

/* Vi sao no da chet:
   - Trinh bien dich da biet kieu. Ban khong can nhac lai.
   - Khi ban doi int thanh long, ban phai doi TEN o moi cho.
     Va neu ban luoi thi ten noi doi.
   - Trinh soan thao hien kieu khi ban tro chuot vao.

   Nhung mot phan cua Hungary VAN co ich: ma hoa Y NGHIA,
   khong phai kieu. Do la "Hungary ung dung": */

int rong_px;        /* pixel */
int rong_em;        /* em */
int cho_ms;         /* mili giay */
int cho_s;          /* giay */

/* Bay gio  cho_ms = cho_s  la mot loi ban NHIN THAY duoc,
   trong khi  int a = int b  thi khong. */

if (!khong_hop_le(x)) { ... }           /* hai lan phu dinh */
if (!chua_khoi_tao) { ... }
if (!bo_qua_kiem_tra) { ... }

/* Nao khong hop le nghia la hop le? Nao chua khoi tao nghia la
   da khoi tao? Moi lan doc la mot lan phai dao nguoc trong dau.

   Dat ten o dang KHANG DINH: */
if (hop_le(x)) { ... }
if (da_khoi_tao) { ... }
if (can_kiem_tra) { ... }

void xu_ly(void *du_lieu);
int  kiem_tra(int x);
Data *lay_du_lieu(void);
void thuc_hien(void);
int  quan_ly_trang_thai(int co);

/* "Xu ly" cai gi? "Kiem tra" dieu gi va tra ve gi?

   Neu ban khong dat duoc mot cai ten cu the cho ham, thuong la
   vi ham do lam QUA NHIEU viec. Ten chung chung la mot mui
   thiet ke, khong chi la mot van de tham my. */

void don_hang_tinh_thue(DonHang *d);
int  email_dung_dinh_dang(const char *s);
CauHinh *cau_hinh_doc_tu_tep(const char *duong_dan);