NCS 301 DATA STRUCTURE USING C

Size: px

Start display at page:

Download "NCS 301 DATA STRUCTURE USING C"

Mervyn Cook
6 years ago
Views:

1 NCS Data Structure Using C -8- NCS DATA STRUCTURE USING C Unit- Part- Stack Hammad Mashkoor Lari Assistant Professor Allenhouse Institute of Technology Introduction Stack is a non primitive linear data structure. Addition of new data item and deletion of already existing data item is done from only one end known as top of stack. Stack is also called Last-in-First-Out(LIFO) type of list. Example:-Plates in marriage party. Subject Notes by Hammad Lari

2 NCS Data Structure Using C -8- Stack Stack empty Top Top= Stack top increases during insertion Top= Top= Stack initially Top= Top= Top= deleted Top=- deleted deleted Stack top decreases during deletion Stack Implementation It can be implemented in two ways: a) Static implementation-uses arrays to create stack. Not so efficient with respect to memory utilization. b) Dynamic implementation-also called linked list representation and uses pointers to implement stack type. Operations on Stack Basic operations on stack are. PUSH-adding new element to top of stack is called push. After every push operation the top is incremented by. In case array is full and no new element can be accommodated it is called STACK-FULL(STACK- OVERFLOW).. POP-process of deleting an element from top of stack is called Pop. After every pop operation stack is decremented by. if there is no element in stack and pop is performed then this will result into STACK UNDERFLOW. Subject Notes by Hammad Lari

3 NCS Data Structure Using C -8- Stack Terminology. Context: the environment in which function executes, includes argument values, local variables, global variables.. Stack frames: the data structure containing all data(arguments, local variables, return address). MAXSIZE: maximum size of stack. TOP: top of stack. Stack: array of MAXSIZE 6. Underflow 7. Overflow Algorithm for Push and Pop Algorithm Push (stack[maxsize], item) Initialize set top=-; If top<max size - then Read,Item Set top=top+; Set stack[top]= item Else Print stack overflow Algorithm Pop (stack[maxsize], item) If top>= Set item =stack[top] Set top=top- Print deleted item Else Stack underflows Subject Notes by Hammad Lari

4 NCS Data Structure Using C -8- Algorithm for Push and Pop Algorithm Push (stack[maxsize], item). [stack already filled?]if top=max then print overflow and return. Set top=top+. Set stack[top]=item. return Algorithm Pop (stack[maxsize], item). [stack has an item to be removed?]if top= then underflow and returm. Set item=stack[top]. Set top=top-. return Functions for Push and Pop using Array int stack[max]; int top=-; void push() int item; if(top==max-) else printf("stack is full"); getch(); exit(); printf("element to insert\t"); scanf("%d",&item); top=top+; stack[top]=item; printf("\n\ninsert is success\n\n"); int pop() int item; int i; if(top==-) printf("stack is empty"); getch(); exit(); else item=stack[top]; top=top-; return(item); void display() int i; printf("stack elements:"); for(i=top;i>=;i--) printf("%d\t",stack[i]); Subject Notes by Hammad Lari

5 NCS Data Structure Using C -8- Minimizing Overflow Underflow depends on given algo and given data (no direct control by programmer) Overflow depends upon arbitrary choice of programmer for amount of memory space reserved for stack. Stack involves a time space trade off(reserving great deal of space for each stack will decrease the no of times overflow may occur but its expensive use of space, reserving a small amount of space may increase the number of times overflow occurs but time for resolving an overflow may be more expensive) Example-remedy for minimizing overflow StackA with n elements StackB with n elements Stack with n+n Stack[]=bottom of stacka and let A grow to right Stack[n]=bottom of stackb and let B grow to left N- N- N- n Functions for Push using Pointer/Linked List struct stack int no; struct stack *next; *top=null; typedef struct stack st; void push() st *node; node=(st*)malloc(sizeof(st)); printf("enter number"); scanf("%d",&node->no); printf("node=%d",node); node->next=top; top=node; printf("top=%d",top); Subject Notes by Hammad Lari

6 NCS Data Structure Using C -8- Functions for Pop using Pointer/Linked List int pop() st *temp; temp=top; printf("temp=%d",temp); if(top==null) printf("stack is empty"); getch(); exit(); else top=top->next; printf("%d",top); free(temp); return(temp->no); void display() st *temp; temp=top; while(temp->next!=null) printf("\nno= %d",temp->no); temp=temp->next; printf("\nno=%d",temp->no); Application of Stacks. Stack Frames-programs compiled from modern high level languages make use of a stack frame for working memory of each procedure or function invocation.eg-recursion stack. Reversing a string-pushing individual characters into stack of full line and then popped out individually.. Calculation of postfix expression Three notations for an mathematical expression are-. Infix- A+B. Prefix- +AB(polish notation in honour of mathematician Jan Lukasiewicz). Postfix- AB+(reverse polish notation) Subject Notes by Hammad Lari 6

7 NCS Data Structure Using C -8- Class Website Subject Notes by Hammad Lari 7

Associate Professor Dr. Raed Ibraheem Hamed

Associate Professor Dr. Raed Ibraheem Hamed University of Human Development, College of Science and Technology Computer Science Department 2015 2016 1 What this Lecture is about: Stack Structure Stack