Computer Programming for Engineering Applica4ons. Intro to Programming 10/17/13 ECE 175. The Stack Data Structure. Examples from Real Life

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Computer Programming for Engineering Applica4ons ECE 175 Intro to Programming The Stack Data

inserted, and deleted in a special way Stacks follow the Last in First out (LiFo) principle

Very simple implementa4on No need for addresses for every element in the memory, just handle

1 Computer Programming for Engineering Applica4ons ECE 175 Intro to Programming The Stack Data Structure Stack: An alloca4on of memory to store data (usually temporary data) Data are inserted, and deleted in a special way Stacks follow the Last in First out (LiFo) principle Why would we want to restrict the way data is accessed? Very simple implementa4on No need for addresses for every element in the memory, just handle the top most element Intui4ve for many computer opera4ons 10/16/13 ECE Examples from Real Life Your midterm exams 10/16/13 ECE

Example from Computer SoVware Use of stacks in sovware The undo buxon Undo buxon picture The undo buxon Use of stacks in sovware Make list PowerPoint 4tle 10/16/13 ECE 175 4 The Push and Pop

2 Example from Computer SoVware Use of stacks in sovware The undo buxon Undo buxon picture The undo buxon Use of stacks in sovware Make list PowerPoint 4tle 10/16/13 ECE The Push and Pop Opera4ons Push Opera4on: Pushes the element on the stack Img Source: Wikipedia Pop: Pops the topmost element of the stack 10/16/13 ECE Using an Array to Represent a stack top (index) element 10/16/13 ECE

3 Stack Opera4on Flowchart input Stack empty YES Is stack empty? POP Ac4on? NO PUSH POP element Read element Decrement top pointer Is stack full? YES Stack is full NO PUSH element to the stack Increment top pointer 10/16/13 ECE Stack Implementa4on #include<stdio.h> #define STACK_SIZE 5 #define EMPTY 0 int push(int x[], int element, int top); int pop(int x[], int top); int main(void) { int i, element; // temporary storage of value read int stack[stack_size]; // array for emulating stack int stack_top=0; for (i=0; i<6; i++) { printf("enter an integer:"); scanf("%d", &element); stack_top=push(stack, element, stack_top); for (i=0; i<6; i++) stack_top=pop(stack, stack_top); return(0); 10/17/13 ECE The PUSH Func4on Adding an element to the stack int push(int x[], int element, int top) { // pushes an element into the stack if (top==stack_size) { // if stack is full printf("the stack is full\n"); return top; else { x[top]=element; // push number to stack printf("%d was pushed into the stack\n", element); return ++top; // update index of top 10/17/13 ECE

4 The POP Func4on Removing an element from the stack int pop(int x[], int top) { // pops an element from the stack if (top==empty) // if stack empty { printf("the stack is empty\n"); return top; // return index on top element else // print the element popped { // point to previous element printf("%d was popped from the stack\n", x[top-1]); return top-1; // return index on top element 10/16/13 ECE Stack Implementa4on - Pointers #include<stdio.h> #define STACK_SIZE 5 int *push(int *x, int element, int *top);// function returns a pointer int *pop(int *x, int *top); // function returns a pointer int main(void) { int i, element; // temporary storage of value read int stack[stack_size]; // array for emulating stack int *top_p=&stack[0]; // pointer to the first empty element for (i=0; i<6; i++) { printf("enter an integer:"); scanf("%d", &element); top_p=push(stack, element, top_p); for (i=0; i<6; i++) top_p=pop(stack, top_p); return(0); 10/16/13 ECE The PUSH Func4on - Pointers Adding an element to the stack int *push(int *x, int element, int *top) { // pushes an element into the stack if (top==x+stack_size) { // if stack is full printf("the stack is full\n"); return top; else { *top=element; // push number to stack printf("%d was pushed into the stack\n", element); return ++top; // return pointer to next empty element 10/16/13 ECE

$The POP Func4on - Pointers Removing an element from the stack int *pop(int *x, int *top) { // pops an element from the stack if (top==x) // if stack empty { printf("the stack is empty\n"); return$

5 The POP Func4on - Pointers Removing an element from the stack int *pop(int *x, int *top) { // pops an element from the stack if (top==x) // if stack empty { printf("the stack is empty\n"); return top; // return pointer else // print the element popped { // point to previous element printf("%d was popped from the stack\n", *(--top)); return top; // return pointer 10/16/13 ECE The Queue Data Structure Queue: An alloca4on of memory to store data (usually temporary data) Data are inserted, and deleted in a special way Queues follow the First in First out (FiFo) principle Why would we want to restrict the way data is accessed? Very simple implementa4on No need for addresses for every element in the memory, just handle the first inserted element Intui4ve for many computer opera4ons 10/16/13 ECE Queues in real life Wai4ng queues for servicing people queue push pop 10/16/13 ECE

6 Queues in computer systems Buffers for servicing jobs in an Opera4ng system Job 3 Job 2 Job 1 Servicing packet transmissions in networks Packet 3 Packet 2 Packet 1 10/16/13 ECE Queue Opera4on Flowchart input queue empty YES Is queue empty? POP Ac4on? NO PUSH POP element Read element Move remaining elements Is queue full? YES queue is full Update pointer NO PUSH element to the queue Update pointer 10/16/13 ECE Queue Implementa4on #include<stdio.h> #define QSIZE 5 int push(int x[], int element, int last); int pop(int x[], int last); void move_forward(int x[], int last); // Adding one element to the queue int main(void) { int i, element; // temporary storage of value read; int queue[qsize]; // array for emulating stack int queue_last=queue[0]; for (i=0; i<6; i++) { printf("enter an integer:"); scanf("%d", &element); queue_last=push(queue, element, queue_last); for (i=0; i<6; i++) queue_last=pop(queue, queue_last); return(0); 10/17/13 ECE

7 The PUSH func4on int push(int x[], int element, int last) { // pushes an element into the queue if (last==qsize) "{ // if queue is full printf("the queue is full\n"); return last; else { x[last]=element; // push number printf("%d was pushed into the queue\n", element); return ++last; // return index of next empty element 10/17/13 ECE The POP Func4on int pop(int x[], int last) { // prints the last element and adjusts the queue pointer "if (last==0) // if queue empty "{ printf("the queue is empty\n"); " return last; " "else // print the element popped "{ // point to previous element printf("%d was poped from the queue\n", x[0]); move_forward(x,last); " return --last; // return pointer void move_forward(int x[], int last) { // advances all elements of the queue one place backwards int i=0; // pointer to an integer while (i<last-1) // while not reached the end of the queue { x[i]=x[i+1]; // move one number up i++; 10/17/13 ECE Queue Implementa4on - Pointers #include<stdio.h> #define QSIZE 5 int *push(int *x, int element, int *last);//pointer to the first empty queue element int *pop(int *x, int *last); // pointer to the first empty queue element void move_forward(int *x, int *last); // moving all elements forward int main(void) { int i, element; // temporary storage of value read; int queue[qsize]; // array for emulating stack int *q_pointer=&queue[0]; for (i=0; i<6; i++) { printf("give me an integer:"); scanf("%d", &element); q_pointer=push(queue, element, q_pointer); for (i=0; i<6; i++) q_pointer=pop(queue, q_pointer); return(0); 10/16/13 ECE

8 The PUSH func4on - Pointers int *push(int *x, int element, int *last) { // pushes an element into the queue if (last==x+qsize) "{ // if queue is full printf("the queue is full\n"); return last; else { *last=element; // push number printf("%d was pushed into the queue\n", element); return ++last; // return pointer to next empty element 10/16/13 ECE The POP Func4on - Pointers int *pop(int *x, int *last) { // prints the last element and adjusts the queue pointer "if (last==x) // if queue empty "{ printf("the queue is empty\n"); return last; " else // print the element popped "{ // point to previous element printf("%d was poped from the queue\n", *x); move_forward(x,last); " return --last; // return pointer void move_forward(int *x, int *last) { // advances all elements of the queue one place backwards int *i=x; // pointer to an integer while (i<last-1) // while not reached the end of the queue { *i=*(i+1); // move one number up i++; 10/16/13 ECE

Data Structures & Algorithm Analysis. Lecturer: Souad Alonazi

Data Structures & Algorithm Analysis Lec(3) Stacks Lecturer: Souad Alonazi What is a stack? Stores a set of elements in a particular order Stack principle: LAST IN FIRST OUT = LIFO It means: the last element