C_chap12_105700.ppt"Arrays: Efficient Data Structures for Computing & Storage"

 2000 Prentice Hall, Inc. All rights reserved.
Chapter 12 – Data Structures
Outline
12.1 Introduction
12.2 Self-Referential Structures
12.3 Dynamic Memory Allocation
12.4 Linked Lists
12.5 Stacks
12.6 Queues
12.7 Trees

12.1 Introduction
• Dynamic data structures - grow and shrink during
execution
• Linked lists - insertions and removals made anywhere
• Stacks - insertions and removals made only at top of stack
• Queues - insertions made at the back and removals made
from the front
• Binary trees - high-speed searching and sorting of data and
efficient elimination of duplicate data items

12.2 Self-Referential Structures
• Self-referential structures
– Structure that contains a pointer to a structure of the same type
– Can be linked together to form useful data structures such as lists,
queues, stacks and trees
– Terminated with a NULL pointer (0)
• Two self-referential structure objects linked together
10
15
NULL pointer (points to nothing)
Data member
and pointer

12.2 Self-Referential Classes (II)
struct node {
int data;
struct node *nextPtr;
}
• nextPtr - points to an object of type node
– Referred to as a link – ties one node to another node

12.3 Dynamic Memory Allocation
• Dynamic memory allocation
– Obtain and release memory during execution
• malloc
– Takes number of bytes to allocate
• Use sizeof to determine the size of an object
– Returns pointer of type void *
• A void * pointer may be assigned to any pointer
• If no memory available, returns NULL
– newPtr = malloc( sizeof( struct node ) );
• free
– Deallocates memory allocated by malloc
– Takes a pointer as an argument
– free (newPtr);

12.4 Linked Lists
• Linked list
– Linear collection of self-referential class objects, called nodes,
connected by pointer links
– Accessed via a pointer to the first node of the list
– Subsequent nodes are accessed via the link-pointer member
– Link pointer in the last node is set to null to mark the list’s end
• Use a linked list instead of an array when
– Number of data elements is unpredictable
– List needs to be sorted

12.4 Linked Lists (II)
• Types of linked lists:
– singly linked list
• Begins with a pointer to the first node
• Terminates with a null pointer
• Only traversed in one direction
– circular, singly linked
• Pointer in the last node points back to the first node
– doubly linked list
• Two “start pointers”- first element and last element
• Each node has a forward pointer and a backward pointer
• Allows traversals both forwards and backwards
– circular, doubly linked list
• Forward pointer of the last node points to the first node and
backward pointer of the first node points to the last node

Outline
1. Define struct
1.1 Function
prototypes
1.2 Initialize variables
2. Input choice
1 /* Fig. 12.3: fig12_03.c
2 Operating and maintaining a list */
3 #include <stdio.h>
4 #include <stdlib.h>
5
6 struct listNode { /* self-referential structure */
7 char data;
8 struct listNode *nextPtr;
9 };
10
11 typedef struct listNode ListNode;
12 typedef ListNode *ListNodePtr;
13
14 void insert( ListNodePtr *, char );
15 char delete( ListNodePtr *, char );
16 int isEmpty( ListNodePtr );
17 void printList( ListNodePtr );
18 void instructions( void );
19
20 int main()
21 {
22 ListNodePtr startPtr = NULL;
23 int choice;
24 char item;
25
26 instructions(); /* display the menu */
27 printf( "? " );
28 scanf( "%d", &choice );

Outline
2.1 switch statement
29
30 while ( choice != 3 ) {
31
32 switch ( choice ) {
33 case 1:
34 printf( "Enter a character: " );
35 scanf( "n%c", &item );
36 insert( &startPtr, item );
37 printList( startPtr );
38 break;
39 case 2:
40 if ( !isEmpty( startPtr ) ) {
41 printf( "Enter character to be deleted: " );
43
44 if ( delete( &startPtr, item ) ) {
45 printf( "%c deleted.n", item );
46 printList( startPtr );
47 }
48 else
49 printf( "%c not found.nn", item );
50 }
51 else
52 printf( "List is empty.nn" );
53
54 break;
55 default:
56 printf( "Invalid choice.nn" );
57 instructions();
58 break;
59 }

Outline
3. Function definitions
60
61 printf( "? " );
63 }
64
65 printf( "End of run.n" );
66 return 0;
67 }
68
69 /* Print the instructions */
70 void instructions( void )
71 {
72 printf( "Enter your choice:n"
73 " 1 to insert an element into the list.n"
74 " 2 to delete an element from the list.n"
75 " 3 to end.n" );
76 }
77
78 /* Insert a new value into the list in sorted order */
79 void insert( ListNodePtr *sPtr, char value )
80 {
81 ListNodePtr newPtr, previousPtr, currentPtr;
82
83 newPtr = malloc( sizeof( ListNode ) );
84
85 if ( newPtr != NULL ) { /* is space available */
86 newPtr->data = value;
87 newPtr->nextPtr = NULL;
88
89 previousPtr = NULL;
90 currentPtr = *sPtr;

Outline
91
92 while ( currentPtr != NULL && value > currentPtr->data ) {
93 previousPtr = currentPtr; /* walk to ... */
94 currentPtr = currentPtr->nextPtr; /* ... next node */
95 }
96
97 if ( previousPtr == NULL ) {
98 newPtr->nextPtr = *sPtr;
99 *sPtr = newPtr;
100 }
101 else {
102 previousPtr->nextPtr = newPtr;
103 newPtr->nextPtr = currentPtr;
104 }
105 }
106 else
107 printf( "%c not inserted. No memory available.n", value );
108}
109
110/* Delete a list element */
111char delete( ListNodePtr *sPtr, char value )
112{
113 ListNodePtr previousPtr, currentPtr, tempPtr;
114
115 if ( value == ( *sPtr )->data ) {
116 tempPtr = *sPtr;
117 *sPtr = ( *sPtr )->nextPtr; /* de-thread the node */
118 free( tempPtr ); /* free the de-threaded node */
119 return value;
120 }

Outline
121 else {
122 previousPtr = *sPtr;
123 currentPtr = ( *sPtr )->nextPtr;
124
125 while ( currentPtr != NULL && currentPtr->data != value ) {
126 previousPtr = currentPtr; /* walk to ... */
127 currentPtr = currentPtr->nextPtr; /* ... next node */
128 }
129
130 if ( currentPtr != NULL ) {
131 tempPtr = currentPtr;
132 previousPtr->nextPtr = currentPtr->nextPtr;
133 free( tempPtr );
134 return value;
135 }
136 }
137
138 return '0';
139}
140
141/* Return 1 if the list is empty, 0 otherwise */
142int isEmpty( ListNodePtr sPtr )
143{
144 return sPtr == NULL;
145}
146
147/* Print the list */
148void printList( ListNodePtr currentPtr )
149{
150 if ( currentPtr == NULL )
151 printf( "List is empty.nn" );
152 else {
153 printf( "The list is:n" );

Outline
154
155 while ( currentPtr != NULL ) {
156 printf( "%c --> ", currentPtr->data );
157 currentPtr = currentPtr->nextPtr;
158 }
159
160 printf( "NULLnn" );
161 }
162}

Outline
Program Output
Enter your choice:
1 to insert an element into the list.
2 to delete an element from the list.
3 to end.
? 1
Enter a character: B
The list is:
B --> NULL
? 1
Enter a character: A
The list is:
A --> B --> NULL
? 1
Enter a character: C
The list is:
A --> B --> C --> NULL
? 2
Enter character to be deleted: D
D not found.
? 2
Enter character to be deleted: B
B deleted.
The list is:
A --> C --> NULL

12.5 Stacks
• Stack
– New nodes can be added and removed only at the top
– Similar to a pile of dishes
– Last-in, first-out (LIFO)
– Bottom of stack indicated by a link member to null
– Constrained version of a linked list
• push
– Adds a new node to the top of the stack
• pop
– Removes a node from the top
– Stores the popped value
– Returns true if pop was successful

Outline
1. Define struct
1.1 Function definitions
2. Input choice
1 /* Fig. 12.8: fig12_08.c
2 dynamic stack program */
5
6 struct stackNode { /* self-referential structure */
7 int data;
8 struct stackNode *nextPtr;
9 };
10
11 typedef struct stackNode StackNode;
12 typedef StackNode *StackNodePtr;
13
14 void push( StackNodePtr *, int );
15 int pop( StackNodePtr * );
16 int isEmpty( StackNodePtr );
17 void printStack( StackNodePtr );
19
20 int main()
21 {
22 StackNodePtr stackPtr = NULL; /* points to stack top */
23 int choice, value;
24
25 instructions();
26 printf( "? " );
28

Outline
30
31 switch ( choice ) {
32 case 1: /* push value onto stack */
33 printf( "Enter an integer: " );
34 scanf( "%d", &value );
35 push( &stackPtr, value );
36 printStack( stackPtr );
37 break;
38 case 2: /* pop value off stack */
39 if ( !isEmpty( stackPtr ) )
40 printf( "The popped value is %d.n",
41 pop( &stackPtr ) );
42
43 printStack( stackPtr );
44 break;
45 default:
47 instructions();
48 break;
49 }
50
51 printf( "? " );
53 }
54
56 return 0;
57 }
58

Outline
59 /* Print the instructions */
61 {
62 printf( "Enter choice:n"
63 "1 to push a value on the stackn"
64 "2 to pop a value off the stackn"
65 "3 to end programn" );
66 }
67
68 /* Insert a node at the stack top */
69 void push( StackNodePtr *topPtr, int info )
70 {
71 StackNodePtr newPtr;
72
73 newPtr = malloc( sizeof( StackNode ) );
74 if ( newPtr != NULL ) {
75 newPtr->data = info;
76 newPtr->nextPtr = *topPtr;
77 *topPtr = newPtr;
78 }
79 else
80 printf( "%d not inserted. No memory available.n",
81 info );
82 }
83

Outline
84 /* Remove a node from the stack top */
85 int pop( StackNodePtr *topPtr )
86 {
87 StackNodePtr tempPtr;
88 int popValue;
89
90 tempPtr = *topPtr;
91 popValue = ( *topPtr )->data;
92 *topPtr = ( *topPtr )->nextPtr;
93 free( tempPtr );
94 return popValue;
95 }
96
97 /* Print the stack */
98 void printStack( StackNodePtr currentPtr )
99 {
101 printf( "The stack is empty.nn" );
102 else {
103 printf( "The stack is:n" );
104
106 printf( "%d --> ", currentPtr->data );
108 }
109
111 }
112}
113

Outline
Program Output
114/* Is the stack empty? */
115int isEmpty( StackNodePtr topPtr )
116{
117 return topPtr == NULL;
118}
Enter choice:
1 to push a value on the stack
2 to pop a value off the stack
3 to end program
? 1
Enter an integer: 5
The stack is:
5 --> NULL
? 1
Enter an integer: 6
The stack is:
6 --> 5 --> NULL
? 1
Enter an integer: 4
The stack is:
4 --> 6 --> 5 --> NULL
? 2
The popped value is 4.
The stack is:
6 --> 5 --> NULL

Outline
Program Output
? 2
The stack is:
5 --> NULL
? 2
The stack is empty.
? 2
The stack is empty.
? 4
Invalid choice.
Enter choice:
1 to push a value on the stack
2 to pop a value off the stack
3 to end program
? 3
End of run.

12.6 Queues
• Queue
– Similar to a supermarket checkout line
– First-in, first-out (FIFO)
– Nodes are removed only from the head
– Nodes are inserted only at the tail
• Insert and remove operations
– Enqueue (insert) and dequeue (remove)
• Useful in computing
– Print spooling, packets in networks, file server requests

Outline
1. Define struct
1.1 Function
prototypes
2. Input choice
1 /* Fig. 12.13: fig12_13.c
2 Operating and maintaining a queue */
3
6
7 struct queueNode { /* self-referential structure */
8 char data;
9 struct queueNode *nextPtr;
10 };
11
12 typedef struct queueNode QueueNode;
13 typedef QueueNode *QueueNodePtr;
14
15 /* function prototypes */
16 void printQueue( QueueNodePtr );
17 int isEmpty( QueueNodePtr );
18 char dequeue( QueueNodePtr *, QueueNodePtr * );
19 void enqueue( QueueNodePtr *, QueueNodePtr *, char );
21
22 int main()
23 {
24 QueueNodePtr headPtr = NULL, tailPtr = NULL;
25 int choice;
26 char item;
27
28 instructions();
29 printf( "? " );

Outline
31
33
34 switch( choice ) {
35
36 case 1:
37 printf( "Enter a character: " );
39 enqueue( &headPtr, &tailPtr, item );
40 printQueue( headPtr );
41 break;
42 case 2:
43 if ( !isEmpty( headPtr ) ) {
44 item = dequeue( &headPtr, &tailPtr );
45 printf( "%c has been dequeued.n", item );
46 }
47
48 printQueue( headPtr );
49 break;
50
51 default:
53 instructions();
54 break;
55 }
56
57 printf( "? " );
59 }
60
62 return 0;
63 }
64

Outline
66 {
67 printf ( "Enter your choice:n"
68 " 1 to add an item to the queuen"
69 " 2 to remove an item from the queuen"
70 " 3 to endn" );
71 }
72
73 void enqueue( QueueNodePtr *headPtr, QueueNodePtr *tailPtr,
74 char value )
75 {
76 QueueNodePtr newPtr;
77
78 newPtr = malloc( sizeof( QueueNode ) );
79
80 if ( newPtr != NULL ) {
81 newPtr->data = value;
82 newPtr->nextPtr = NULL;
83
84 if ( isEmpty( *headPtr ) )
85 *headPtr = newPtr;
86 else
87 ( *tailPtr )->nextPtr = newPtr;
88
89 *tailPtr = newPtr;
90 }
91 else
92 printf( "%c not inserted. No memory available.n",
93 value );
94 }
95

Outline
96 char dequeue( QueueNodePtr *headPtr, QueueNodePtr *tailPtr )
97 {
98 char value;
99 QueueNodePtr tempPtr;
100
101 value = ( *headPtr )->data;
102 tempPtr = *headPtr;
103 *headPtr = ( *headPtr )->nextPtr;
104
105 if ( *headPtr == NULL )
106 *tailPtr = NULL;
107
108 free( tempPtr );
109 return value;
110}
111
112int isEmpty( QueueNodePtr headPtr )
113{
114 return headPtr == NULL;
115}
116
117void printQueue( QueueNodePtr currentPtr )
118{
120 printf( "Queue is empty.nn" );
121 else {
122 printf( "The queue is:n" );

Outline
Program Output
123
125 printf( "%c --> ", currentPtr->data );
127 }
128
130 }
131}
Enter your choice:
1 to add an item to the queue
2 to remove an item from the queue
3 to end
? 1
Enter a character: A
The queue is:
A --> NULL
? 1
Enter a character: B
The queue is:
A --> B --> NULL
? 1
Enter a character: C
The queue is:
A --> B --> C --> NULL

Outline
Program Output
? 2
A has been dequeued.
The queue is:
B --> C --> NULL
? 2
B has been dequeued.
The queue is:
C --> NULL
? 2
C has been dequeued.
Queue is empty.
? 2
Queue is empty.
? 4
Invalid choice.
Enter your choice:
1 to add an item to the queue
2 to remove an item from the queue
3 to end
? 3
End of run.

12.7 Trees
• Tree nodes contain two or more links
– All other data structures we have discussed only contain one
• Binary trees
– All nodes contain two links
• None, one, or both of which may be NULL
– The root node is the first node in a tree.
– Each link in the root node refers to a child
– A node with no children is called a leaf node
B
A D
C

12.7 Trees (II)
• Binary search tree
– Values in left subtree less than parent
– Values in right subtree greater than parent
– Facilitates duplicate elimination
– Fast searches - for a balanced tree, maximum of log n
comparisons
47
25 77
11 43 65 93
68
7 17 31 44
2

12.7 Trees (III)
• Tree traversals:
– Inorder traversal - prints the node values in ascending
order
1. Traverse the left subtree with an inorder traversal.
2. Process the value in the node (i.e., print the node value).
3. Traverse the right subtree with an inorder traversal.
– Preorder traversal:
1. Process the value in the node.
2. Traverse the left subtree with a preorder traversal.
3. Traverse the right subtree with a preorder traversal.
– Postorder traversal:
1. Traverse the left subtree with a postorder traversal.
2. Traverse the right subtree with a postorder traversal.
3. Process the value in the node.

Outline
1. Define structure
1.1 Function
prototypes
1 /* Fig. 12.19: fig12_19.c
2 Create a binary tree and traverse it
3 preorder, inorder, and postorder */
6 #include <time.h>
7
8 struct treeNode {
9 struct treeNode *leftPtr;
10 int data;
11 struct treeNode *rightPtr;
12 };
13
14 typedef struct treeNode TreeNode;
15 typedef TreeNode *TreeNodePtr;
16
17 void insertNode( TreeNodePtr *, int );
18 void inOrder( TreeNodePtr );
19 void preOrder( TreeNodePtr );
20 void postOrder( TreeNodePtr );
21
22 int main()
23 {
24 int i, item;
25 TreeNodePtr rootPtr = NULL;
26
27 srand( time( NULL ) );
28

Outline
1.3 Insert random
elements
2. Function calls
29 /* insert random values between 1 and 15 in the tree */
30 printf( "The numbers being placed in the tree are:n" );
31
32 for ( i = 1; i <= 10; i++ ) {
33 item = rand() % 15;
34 printf( "%3d", item );
35 insertNode( &rootPtr, item );
36 }
37
38 /* traverse the tree preOrder */
39 printf( "nnThe preOrder traversal is:n" );
40 preOrder( rootPtr );
41
42 /* traverse the tree inOrder */
43 printf( "nnThe inOrder traversal is:n" );
44 inOrder( rootPtr );
45
46 /* traverse the tree postOrder */
47 printf( "nnThe postOrder traversal is:n" );
48 postOrder( rootPtr );
49
50 return 0;
51 }
52
53 void insertNode( TreeNodePtr *treePtr, int value )
54 {
55 if ( *treePtr == NULL ) { /* *treePtr is NULL */
56 *treePtr = malloc( sizeof( TreeNode ) );
57
58 if ( *treePtr != NULL ) {
59 ( *treePtr )->data = value;
60 ( *treePtr )->leftPtr = NULL;
61 ( *treePtr )->rightPtr = NULL;
62 }

Outline
63 else
64 printf( "%d not inserted. No memory available.n",
65 value );
66 }
67 else
68 if ( value < ( *treePtr )->data )
69 insertNode( &( ( *treePtr )->leftPtr ), value );
70 else if ( value > ( *treePtr )->data )
71 insertNode( &( ( *treePtr )->rightPtr ), value );
72 else
73 printf( "dup" );
74 }
75
76 void inOrder( TreeNodePtr treePtr )
77 {
78 if ( treePtr != NULL ) {
79 inOrder( treePtr->leftPtr );
80 printf( "%3d", treePtr->data );
81 inOrder( treePtr->rightPtr );
82 }
83 }
84
85 void preOrder( TreeNodePtr treePtr )
86 {
89 preOrder( treePtr->leftPtr );
90 preOrder( treePtr->rightPtr );
91 }
92 }

Outline
Program Output
93
94 void postOrder( TreeNodePtr treePtr )
95 {
97 postOrder( treePtr->leftPtr );
98 postOrder( treePtr->rightPtr );
100 }
101}
The numbers being placed in the tree are:
7 8 0 6 14 1 0dup 13 0dup 7dup
The preOrder traversal is:
7 0 6 1 8 14 13
The inOrder traversal is:
0 1 6 7 8 13 14
The postOrder traversal is:
1 6 0 13 14 8 7

C_chap12_105700.ppt"Arrays: Efficient Data Structures for Computing & Storage"

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