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Extensible Array C and Data Structures Baojian Hua [email protected]

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Extensible Array. C and Data Structures Baojian Hua [email protected]. 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} - PowerPoint PPT Presentation

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Extensible Array

C and Data StructuresBaojian Hua

[email protected]

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

Linear Data Structures Typical operations on linear list :// create an empty listnewList ();// the length of a list llength (list l); // insert element x at position i in l, 0<=i<ninsert (list l, x, i); // return the i-th elementnth (list l, i); // delete the element at position i in l, 0<=i<ndelete (list l, i);// apply function f to each element in lforeach (list l, f);

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

Implementations

Two typical implementation techniques: array-based linked structure-based

We next consider the first, and leave the second to the next slide

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

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)

0 n-1

tail

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;};

0 n-1

array

max

tail

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;}

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

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;}

0 n-1

array

%$&^

@#%$

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;}

0 n-1

array

max

@#%$

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;}

0 n-1

array

max

tail

l

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;}

0 n-1

array

max

tail

l

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;}

0 n-1

array

max

tail

l

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;}

0 n-1

array

max

tail

l

i

temp

Operation: “insert”void insert (list l, poly x, int i){ if (i<0 || i>l->tail) error (“invalid index”);

//move the data …;}

0 n-1

array

max

tail

l

i

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]; …;}

0 n-1

array

max

tail

l

i

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]; …;}

0 n-1

array

max

tail

l

i

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]; …;}

0 n-1

array

max

tail

l

i

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;}

x

0 n-1

array

max

tail

l

i

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)++;} x

0 n-1

array

max

tail

l

i

j

Perfect? What if the initial input arguments

look like this one? direct datamovement willincur an out-of-bound error!

0 n-1

array

max

tail

l

i

Extensible Arrayvoid 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…;}

Extensible Array

0 n-1

array

max

tail

l

i

0 2n-1

i

l->array = realloc (l->array, EXT_FACTOR*(l->max)*sizeof(poly));

n-1

Extensible Array

0 n-1

array

max

tail

l

i

0 2n-1

i

n-1

l->array = realloc (l->array, EXT_FACTOR*(l->max)*sizeof(poly));

Extensible Array

0 n-1

array

max

tail

l

i

0 2n-1

i

l->max *= EXT_FACTOR;

l->array = realloc (l->array, EXT_FACTOR*(l->max)*sizeof(poly));

Extensible Array

array

max

tail

l

0 2n-1

i

n-1

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

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

0 n-1

array

max

tail

l

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