Data Structure. Chapter 4 List (Part II) Department of Communication Engineering National Central University Jhongli, Taiwan.

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1 Data Structure Chapter 4 List (Part II) Angela Chih-Wei Tang Department of Communication Engineering National Central University Jhongli, Taiwan 2009 Spring

2 Outline Polynomials Sparse matrices Doubly linked lists C.E., NCU, Taiwan Angela Chih-Wei Tang,

3 Figure 4.11: Polynomial Representation typedef struct poly_node *poly_pointer; typedef struct poly_node { int coef; int expon; poly_pointer link; ; poly_pointer a, b, d; a a 14 = 3x + 2x b b = x 3x 10x C.E., NCU, Taiwan Angela Chih-Wei Tang,

4 Fig. 4.12: Generating The First Three Terms of d=a+b (1/3) a b d (a) a->exp == b->exp C.E., NCU, Taiwan Angela Chih-Wei Tang,

5 Fig. 4.12: Generating The First Three Terms of d=a+b (2/3) a b d (b) a->exp < b->exp C.E., NCU, Taiwan Angela Chih-Wei Tang,

6 Fig. 4.12: Generating The First Three Terms of d=a+b (3/3) a b (c) a->exp > b->exp d C.E., NCU, Taiwan Angela Chih-Wei Tang,

7 Program 4.10: Add Two Polynomials (1/2) poly_pointer padd(poly_pointer a, poly_pointer b) { /* return a polynomial which is the sum of a and b */ poly_pointer front, rear, temp; int sum; rear = (poly_pointer)malloc(sizeof(poly_node)); if (IS_FULL(rear)){ fprintf(stderr, The memory is full\n ); exit(1) front = rear; while (a &&b) switch (COMPARE(a->expon, b->expon)) { case -1: /* a->expon < b->expon */ attach(b->coef, b->expon, &rear); b = b->link; break; C.E., NCU, Taiwan Angela Chih-Wei Tang,

8 Program 4.10: Add Two Polynomials (2/2) case 0: /* a->expon = b->expon */ sum = a->coef + b->coef; if (sum) attach(sum, a->expon, &rear); a = a->link; b = b->link; break; case 1: /* a->expon > b->expon */ attach(a->coef, a->expon, &rear); a = a->link; /* copy rest of list a and then list b*/ for (; a; a = a->link) attach(a->coef, a->expon, &rear); for (; b; b = b->link) attach(b->coef, b->expon, &rear); rear->link = NULL: /* delete extra initial node */ temp = front; front = front->link; free(temp); return front; C.E., NCU, Taiwan Angela Chih-Wei Tang,

9 Program 4.11: Attach A Node to The End of A List void attach(float coefficient, int exponent, poly_pointer *ptr) { /* create a new node with coef=coefficient and expon=exponent, attach it to the node pointed to by ptr. Ptr is updated to point to this new node */ poly_pointer temp; temp = (poly_pointer)mallc(sizeof(poly_node)); if (IS_FULL(temp)) { fprintf(stderr, The memory is full\n ); exit(1); temp->coef = coefficient; temp->expon = exponent; (*ptr)->link = temp; *ptr = temp; C.E., NCU, Taiwan Angela Chih-Wei Tang,

10 Program 4.12: Erasing A Polynomial void erase(poly_pointer *ptr) { /* erase the polynomial pointed to by ptr */ poly_pointer temp; while (*ptr) { temp = *ptr; *ptr = (*ptr)->link; free(temp); How can we free all the nodes of a polynomial more efficiently? C.E., NCU, Taiwan Angela Chih-Wei Tang,

11 Solution: Circular List!!! ptr ptr = 3x + 2x C.E., NCU, Taiwan Angela Chih-Wei Tang,

12 Program 4.13: get_node Function poly_pointer get_node(void) /* provide a node for use */ { poly_pointer node; if (avail) { node = avail; avail = avail->link; else { node = (poly_pointer) malloc(sizeof(poly_node)); if (IS_FULL(node)) { fprintf(stderr, The memory is full\n ); exit(1); return node; C.E., NCU, Taiwan Angela Chih-Wei Tang,

13 Program 4.14: ret_node Function void ret_node(poly_pointer ptr) { /* return a node to the available list */ ptr->link = avail; avail = ptr; C.E., NCU, Taiwan Angela Chih-Wei Tang,

14 Program 4.15: Erasing A Circular List void cerase(poly_pointer *ptr) { /*erase the circular list ptr */ poly_poitner temp; if (*ptr) { temp = (*ptr)->link; (*ptr)->link = avail; avail = temp; *ptr = NULL; C.E., NCU, Taiwan Angela Chih-Wei Tang,

15 Fig. 4.14: Returning A Circular List to The Avail List ptr avail 3 1 temp avail C.E., NCU, Taiwan Angela Chih-Wei Tang,

16 Fig. 4.15: Polynomial Representations a _ (a) Zero polynomial a _ (b) 3x x C.E., NCU, Taiwan Angela Chih-Wei Tang,

17 Outline Polynomials Sparse matrices Doubly linked lists C.E., NCU, Taiwan Angela Chih-Wei Tang,

18 Node Structure for Sparse Matrices down tag right next downtag row col right value entry i aij j (a) Head node (b) Entry node (c) Setup for a ij Head node i : the head node for both row i and column i Each head node is belonged to three lists: a row list, a column list, and a head node list A 4x4 sparse matrix a C.E., NCU, Taiwan Angela Chih-Wei Tang,

19 Linked Representation of A Sparse Matrix (No Tag Field) a 4 4 H0 H1 H2 H3 H H H H C.E., NCU, Taiwan Angela Chih-Wei Tang,

20 Outline Polynomials Sparse matrices Doubly linked lists C.E., NCU, Taiwan Angela Chih-Wei Tang,

21 Why Doubly Linked Lists? The problems of a singly linked list How can we find the node precedes a node ptr efficiently? How can we efficiently delete a node before a node ptr? Anyway, we need to know its preceding node!!! Head Ptr C.E., NCU, Taiwan Angela Chih-Wei Tang,

22 Doubly Linked Circular List with Head Node A node in a doubly linked list: typedef struct node *node_pointer; typedef struct node { node_pointer llink; element item; node_pointer rlink; ; ptr = ptr->llink->rlink = ptr->rlink->llink Head Node llink item rlink Empty List llink item rlink C.E., NCU, Taiwan Angela Chih-Wei Tang,

23 Program 4.28: Insertion into A Doubly Linked Circular List void dinsert(node_pointer node, node_pointer newnode) { /* insert newnode to the right of node */ newnode->llink = node; newnode->rlink = node->rlink; node->rlink->llink = newnode; node->rlink = newnode; node node newnode C.E., NCU, Taiwan Angela Chih-Wei Tang,

24 Program 4.29: Deletion from A Doubly Linked Circular List void ddelete(node_pointer node, node_pointer deleted) { /* delete from the doubly linked list */ if (node == deleted) else { printf( Deletion of head node not permitted. \n ); deleted->llink->rlink = deleted->rlink; deleted->rlink->llink = deleted->llink; free(deleted); node node C.E., NCU, Taiwan Angela Chih-Wei deleted Tang,

Fall, 2015 Prof. Jungkeun Park

Data Structures t and Algorithms Circular lists / Doubly linked lists Fall, 2015 Prof. Jungkeun Park Copyright Notice: This material is modified version of the lecture slides by Prof. Rada Mihalcea in