CS1301 Data Structures
Unit I INTRODUCTION Introduction Data structure Linked DS Succinct DS Implicit DS Compressed DS Search DS Static and Dynamic DS Persistent DS Concurrent DS Arrays Recursions
Data structure
• a particular way of storing and organizing data in a computer so that it can be used efficiently.
Linked DS• is a data structure which consists of a set of data
records (nodes) linked together and organized by references (links or pointers)
• In linked data structures, the links are usually treated as special data types that can only be compared for equality
• a structure contains a pointer to another instance of the same structure or different structure
• Linking can be done in two ways - Using dynamic allocation and using array index linking
• include linked lists, search trees, expression trees
Linked DS
• Advantages against arrays–more flexibility– saving wasted memory (built
dynamically)– the reference to each node gives us the
information where to find out the next one
–Memory can be utilized more efficiently
Linked DS
• General disadvantages– follow multiple pointers so element
access time varies–may also use more memory
Linked LIST
• Consists of series of node• Each node of the list contains
• the data item• a pointer to the next node
• Flexible space use• Dynamically allocate space for each element
as needed• Include a pointer to the next item
Object
Data Next
Linked LIST
• Types of Linked List– Singly Linked List– Doubly Linked List– Circular Linked List
SINGLY Linked LIST
• Each node contains only one link field pointing to the next node in the list
700 1000 800
550 700 1000 80010 20 30 40
Header
SINGLY Linked LISTCollection structure has a pointer to the list
headInitially NULL
Add first itemAllocate space for nodeSet its data pointer to objectSet Next to NULLSet Head to point to new node
Data Next
object
Head
Collectionnode
SINGLY Linked LISTAdd second item
Allocate space for nodeSet its data pointer to objectSet Next to current HeadSet Head to point to new node
Data Next
object
Head
Collection
nodeData Next
object2
node
SINGLY Linked LIST• Declaration for Linked ListStruct node;typedef struct Node *Listtypedef struct Node *Positionint IsLast (List L);int IsEmpty(List L);position Find(int x, List L);void delete(int x, List L);Struct node{
int element;position next;
};
SINGLY Linked LIST• Routine to insert an element in the listvoid insert(int x, List L, Position P) // insert after position P{Position Newnode;Newnode = malloc(size of(Struct Node));If(Newnode !=NULL){
Newnode Element =X;Newnode Next =PNext;P Next = Newnode;
}}
To insert an element in the list
SINGLY Linked LIST
• Routine to check whether list is empty
int IsEmpty(List L) // returns 1 if L is empty{
if (L Next == NULL)return(1);
}
SINGLY Linked LIST
• Routine to check whether current position is last
int IsLast(position p,List L) // returns 1 if P is the last position in L
{if (P Next == NULL)return(1);
}
SINGLY Linked LIST• Find Routine position Find(int x,List L){//Returns the position of x in L, null if x is not foundPosition P;P= L Next;
while(P!= NULL && PElement!= X)P=PNextreturn P;
}
SINGLY Linked LIST• Find Previous Routine position Findprevious(int x,List L){//Returns the position of the predecessorPosition p;P=L
while(P Next!= NULL && PNextElement!= X)P=PNextreturn P;
}
SINGLY Linked LIST• Find Next Routine position FindNext(int x,List L){//Returns the position of its successorP=L Next
while(P Next!= NULL && PElement!= X)P=PNextreturn PNext;
}
SINGLY Linked LIST• Routine to delete an element from the listVoid Delete(int x, List L){// Delete the first occurrence of X from the list
position P, temp;P= Findprevious(x,L);If(!IsLast(P,L)){
Temp=P Next;PNext = Temp Nextfree(temp);
}}
SINGLY Linked LIST• Routine to delete the listVoid DeleteList(List L){
position P, Temp;P= LNext ; LNext = NULL;while(P!=NULL){
Temp=P Next;free(P);P=Temp;
}}
DoUBLY Linked LIST
• Each node has three fields– Data field– Forward Link(FLINK)– Backward link(BLINK)
• FLINK points to the successor node in the list
• BLINK points to the predecessor nodeBLINK Data FLINK
Doubly Linked LIST
L10 20
Header
30
Structure DeclarationStruct Node{Int element;Struct Node *FLINK;Struct Node *BLINK;}
DoUBLY Linked LISTRoutine to insert an element in a doubly linked listVoid insert(int x, list l, position p){
struct Node *Newnode;Newnode= malloc(size of(Struct Node));If (Newnode !=NULL){Newnode Element =x;Newnode Flink = p Flink;P flink blink =Newnode;P Flink = Newnode;Newnode Blink = p;}
}
DoUBLY Linked LIST
DoUBLY Linked LIST
DoUBLY Linked LIST
• Advantages– Deletion operation is easier– Finding predecessor & successor of a
node is easier
• Disadvantages–More memory space required since it
has two pointers
CIRCULAR Linked LIST
• Pointer of last node points to the first node
• Types–Singly Linked Circular List–Doubly Linked circular List
CIRCULAR Linked LIST
• Singly Linked Circular List–Last node of the list points to the first node
CIRCULAR Linked LIST
• Doubly Linked Circular List– Doubly linked list– Forward link of last node points to the first node– Backward link of the first node points to the last
node of the list
CIRCULAR Linked LIST
• Advantages–Allows to traverse the list starting at
any point–Allows quick access to the first and
last records–Circular doubly linked list allows the
list to traverse in either directions.
POINTERS and arrays• Special variables which contain the address of
another memory locationint arr[4] = {2,4,6,8};
• arr acts as constant pointer pointing to first element
• arr= &arr[0]=100 arr[0] arr[1] arr[2] arr[3]
100 102 104 106
• & is the address operator, represents address of the variable
• %u – obtaining the address
2 4 6 8
POINTERS
main(){
int a=2;printf(“value of a=%d”,a); printf(“addressof a=%u”,&a);
} a – variable namevalue of a or value at address 1000
1000 - address
2
• * operator is the value of at the address operator• Pointer variable declaration - * should preced
variable nameint *b;b=&a;
• b is the variable which contains the address of variable a as its value
• Pointer variable that stores the address of a pointer variableint a=2; int *b;int **c; b=&a; c=&b;
• C has been declared as pointer to pointer variable which contains the address of pointer variable b
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