1 / 31

Extensible Array

Extensible Array. C and Data Structures Baojian Hua bjhua@ustc.edu.cn. Linear Data Structures. A linear list (list) consists of: a collection of data elements e1, e2, … , en elements are ordered: e1 ≤ e2 ≤ … ≤ en ei is called an predecessor of e_{i+1}

valentine-miles
Télécharger la présentation

Extensible Array

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Extensible Array C and Data Structures Baojian Hua bjhua@ustc.edu.cn

  2. Linear Data Structures • A linear list (list) consists of: • a collection of data elements • e1, e2, …, en • elements are ordered: • e1≤e2 ≤…≤ en • ei is called an predecessor of e_{i+1} • e_{i+1} is called a successor of ei • every element has at most one successor and one predecessor

  3. Linear Data Structures • Typical operations on linear list : // create an empty list newList (); // the length of a list l length (list l); // insert element x at position i in l, 0<=i<n insert (list l, x, i); // return the i-th element nth (list l, i); // delete the element at position i in l, 0<=i<n delete (list l, i); // apply function f to each element in l foreach (list l, f);

  4. Polymorphic Abstract Data Types in C // in “list.h” #ifndef LIST_H #define LIST_H typedef struct listStruct *list; list newList (); int length (list l); poly nth (list l, int n); // “poly”? void insert (list l, poly x, int i); poly delete (list l, int i); void foreach (list l, void (*f)(poly)); #endif

  5. Implementations • Two typical implementation techniques: • array-based • linked structure-based • We next consider the first, and leave the second to the next slide

  6. Implementation Using Array • The straightforward method to implement this interface (ADT) is to use an array • and the array may not be full, so we must keep a “tail” tag to record its tail (the position of its last elements) 0 n-1

  7. Implementation Using Array • The straightforward method to implement this interface is to use an array • and the array may not be full, so we must keep a “tail” tag to record its tail (the position of its last elements) tail 0 n-1

  8. Array-based Implementation // Combine these above observations, we have: // in file “arrayList.c” #include <stdlib.h> #include “list.h” #define INIT_LENGTH 32 #define EXT_FACTOR 2 struct listStruct { poly *array; int max; int tail; }; l array max tail 0 n-1

  9. Operation: “newList” list newList () { list l = (list)malloc (sizeof (*l)); l->array = malloc (INIT_LENTH * sizeof(poly)); l->max = INIT_LENTH; l->tail = 0; return l; }

  10. l $#%& %$&^ @#%$ Operation: “newList” list newList () { list l = (list)malloc (sizeof (*l)); l->array = malloc (INIT_LENTH * sizeof(poly)); l->max = INIT_LENTH; l->tail = 0; return l; }

  11. l array %$&^ @#%$ 0 n-1 Operation: “newList” list newList () { list l = (list)malloc (sizeof (*l)); l->array = malloc (INIT_LENTH * sizeof(poly)); l->max = INIT_LENTH; l->tail = 0; return l; }

  12. Operation: “newList” list newList () { list l = (list)malloc (sizeof (*l)); l->array = malloc (INIT_LENTH * sizeof(poly)); l->max = INIT_LENTH ; l->tail = 0; return l; } l array max @#%$ 0 n-1

  13. Operation: “newList” list newList () { list l = (list)malloc (sizeof (*l)); l->array = malloc (INIT_LENTH * sizeof(poly)); l->max = INIT_LENTH ; l->tail = 0; return l; } l array max tail 0 n-1

  14. Operation: “length” int length (list l) { // note that we omit such checks in the next // for clarity. However, You should always do // such kind of checks in your code. assert(l); return l->tail; } l array max tail 0 n-1

  15. Operation: “nth” poly nth (list l, int i) { if (i<0 || i>=l->tail) error (“invalid index”); poly temp; temp = *((l->array)+i); return temp; } l array max tail 0 n-1

  16. temp Operation: “nth” poly nth (list l, int i) { if (i<0 || i>=l->tail) error (“invalid index”); poly temp; temp = *((l->array)+i); return temp; } l array max tail i 0 n-1

  17. Operation: “insert” void insert (list l, poly x, int i) { if (i<0 || i>l->tail) error (“invalid index”); //move the data …; } l array max tail i 0 n-1

  18. j Operation: “insert” void insert (list l, poly x, int i) { if (i<0 || i>l->tail) error (“invalid index”); for (int j=l->tail; j>i; j--) (l->array)[j] = (l->array)[j-1]; …; } l array max tail i 0 n-1

  19. j Operation: “insert” void insert (list l, poly x, int i) { if (i<0 || i>l->tail) error (“invalid index”); for (int j=l->tail; j>i; j--) (l->array)[j] = (l->array)[j-1]; …; } l array max tail i 0 n-1

  20. j Operation: “insert” void insert (list l, poly x, int i) { if (i<0 || i>l->tail) error (“invalid index”); for (int j=l->tail; j>i; j--) (l->array)[j] = (l->array)[j-1]; …; } l array max tail i 0 n-1

  21. j Operation: “insert” void insert (list l, void *x, int i) { if (i<0 || i>l->tail) error (“invalid index”); for (int j=l->tail; j>i; j--) (l->array)[j] = (l->array)[j-1]; (l->array)[i] = x; } l array max tail i x 0 n-1

  22. j Operation: “insert” void insert (list l, void *x, int i) { if (i<0 || i>l->tail) error (“invalid index”); for (int j=l->tail; j>i; j--) (l->array)[j] = (l->array)[j-1]; (l->array)[i] = x; (l->tail)++; } l array max tail i x 0 n-1

  23. Perfect? • What if the initial input arguments look like this one? • direct data movement will incur an out-of-bound error! l array max tail i 0 n-1

  24. Extensible Array void insert (list l, poly x, int i) { if (i<0 || i>l->tail) error (“invalid index”); // if l is full, extend l->array by a factor… if (l->tail==l->max) { l->array = realloc (l->array, EXT_FACTOR*(l->max)*sizeof(poly)); l->max *= EXT_FACTOR; } // data movement as discussed above…; }

  25. Extensible Array l->array = realloc (l->array, EXT_FACTOR*(l->max)*sizeof(poly)); l array max tail i 0 n-1 i n-1 0 2n-1

  26. Extensible Array l->array = realloc (l->array, EXT_FACTOR*(l->max)*sizeof(poly)); l array max tail i 0 n-1 i n-1 0 2n-1

  27. Extensible Array l->array = realloc (l->array, EXT_FACTOR*(l->max)*sizeof(poly)); l array l->max *= EXT_FACTOR; max tail i 0 n-1 i 0 2n-1

  28. Extensible Array l array max tail i n-1 0 2n-1

  29. Operation: “delete” • The “delete” operation is reverse operation of the “insert” operation • also involves data movement • should we shrink the extensible array, when there are few elements in it (say ½ data item left)? • See the programming assignment

  30. Operation: “foreach” void foreach (list l, void (*f)(poly)) { for (int i=0; i<l->tail; i++) f (*(l->array + i)); return; } l array max tail 0 n-1

  31. Summary • Linear list ADT: • a collection of ordered data element • each item has no more than one successor or predecessor • Extensible array-based implementation • maintain internally a dynamically extensible array • bad performance with insert or delete • space waste

More Related