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QUEUE

QUEUE. Pertemuan ke-6 T 0026. D. D. R. R. C. C. C. R. B. B. B. B. R. F. A. A. A. A. R. F. F. F. F. Queue. Bentuk khusus dari ordered list Data di insert di akhir list Data di delete di awal list. Queue sebagai ADT. Misal, queue Q terdiri dari n elemen

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QUEUE

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  1. QUEUE Pertemuan ke-6T 0026

  2. D D R R C C C R B B B B R F A A A A R F F F F Queue • Bentuk khusus dari ordered list • Data di insert di akhir list Data di delete di awal list

  3. Queue sebagai ADT Misal, queue Q terdiri dari n elemen Q = ( ao , a1 , … , ai , ai+1 , …, an-1 ) Elemen paling depan FRONT Elemen paling belakang REAR • ao : elemen yang diinsert pertama kali • an-1 : elemen yang diinsert terakhir

  4. Representasi Queue • Yang paling sederhana : array 1-D • Disebut Sequential Queue • 2 variabel indikator REAR dan FRONT #define MAX_QUEUE_SIZE 100 eltype queue[MAX_QUEUE_SIZE]; int rear = -1; int front = -1;

  5. Aplikasi Queue dengan Array 1-D

  6. Sequential Queue : Add Queue void addq (int *rear, eltype item) { if (*rear == MAX_QUEUE_SIZE-1) { printf (“Queue penuh\n”); return; } queue[++*rear] = item; } /* indeks rear di-increment sebelum insert data baru */

  7. Sequential Queue : Delete Queue eltype deleteq(int *front, int rear){ if (front == rear) { printf (“queue empty\n”); return; } return queue(++*front); } /*indeks front di-increment sebelum passing nilai yang disimpan di queue */

  8. Kekurangan Sequential Queue • Setelah beberapa data insert dan delete dari queue, REAR dan FRONT bergerak ke kanan, hingga REAR mencapai MAX_QUEUE_SIZE-1. • Jika REAR mencapai maksimum, queue akan dideteksi PENUH, meskipun beberapa lokasi di depan FRONT kosong. • Solusi : elemen queue harus digeser ke depan shg FRONT=-1 dan REAR != MAX_QUEUE_SIZE-1 • Tetapi perlu waktu untuk menggeser elemen satu persatu. • Lebih baik gunakan circular array untuk queue

  9. [2] [2] [3] [3] F=4 R=4 [1] [1] [4] [4] [0] [0] [5] [5] F=0 R=0 Circular Queue : Empty Empty : front = rear

  10. Full : front = (rear + 1) % MAX_QUEUE_SIZE R F [2] [2] [3] [3] J2 J3 J8 J1 J4 [1] [1] [4] [4] J7 J4 J5 J6 J5 [0] [0] [5] [5] F R Circular Queue : Full

  11. [2] [3] J1 [1] [4] R [0] [5] F Circular Queue : Insert [2] [3] R J2 J1 [1] [4] [0] [5] F Insert : REAR berubah, FRONT tetap *rear = (*rear+1) % MAX_QUEUE_SIZE

  12. R F [2] [2] [3] [3] J8 J8 [1] [1] [4] [4] J7 J7 J4 J4 J6 J6 J5 J5 [0] [0] [5] [5] Circular Queue : Delete R Delete : FRONT berubah, REAR tetap *front = (*front+1) % MAX_QUEUE_SIZE F

  13. Circular Queue : Add Queue void addq(int front,int *rear, eltype item){ *rear = (*rear+1)%MAX_QUEUE_SIZE; if (front = *rear) { printf (“Queue full\n”); return; } queue[*rear] = item; }

  14. Circular Queue : Delete Queue eltype deleteq (int *front, int rear){ eltype item; if (*front == rear) { printf (“Queue empty\n”); return; } *front = (*front+1)%MAX_QUEUE_SIZE; return queue[*front]; }

  15. Implementasi Queue dengan Single Linked-List Typedef struct elqueue { char name[10]; float ip; struct elqueue *link; } nama ip link nama ip nama ip front link link Tono 3.8 Dewi 4.0 Ani 3.7 NULL rear

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