Chapter 3 Stack. Books: ISRD Group New Delhi Data structure Using C

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Jesse Terry
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1 C302.3 Develp prgrams using cncept f stack. Bks: ISRD Grup New Delhi Data structure Using C Tata McGraw Hill What is Stack Data Structure? Stack is an abstract data type with a bunded(predefined) capacity. It is a simple data structure that allws adding and remving elements in a particular rder. Every time an element is added, it ges n the tp f the stack and the nly element that can be remved is the element that is at the tp f the stack, just like a pile f bjects. It is a linear data structure where each element fllws a particular rder knwn as LIFO (Last In First Out). Stack has tw peratins. Fr additin f element there is Push and fr remval f element there is Pp. Operatins perfrmed by stack are as fllws: Push: It adds the element t the cllectin. Pp: It remves the mst recently added element. Tp r Peek: It returns the tp element f array. isempty: It returns true if stack is empty else return false.

Stack Representatin The fllwing diagram depicts a stack and its peratins A stack can be implemented by means f Array, Structure, Pinter, and Linked List.

2 Stack Representatin The fllwing diagram depicts a stack and its peratins A stack can be implemented by means f Array, Structure, Pinter, and Linked List. Stack can either be a fixed size ne r it may have a sense f dynamic resizing. Here, we are ging t implement stack using arrays, which makes it a fixed size stack implementatin. Basic features f Stack 1. Stack is an rdered list f similar data type. 2. Stack is a LIFO(Last in First ut) structure r we can say FILO(First in Last ut). 3. push() functin is used t insert new elements int the Stack and pp() functin is used t remve an element frm the stack. Bth insertin and remval are allwed at nly ne end f Stack called Tp.

3 4. Stack is said t be in Overflw state when it is cmpletely full and is said t be in Underflw state if it is cmpletely empty. Applicatins f Stack Real wrld applicatin: Pile f plates Wearing r remving bangles. Reverse f a wrd Stack f bks etc. Technical applicatin: Expressin Evlutin Expressin Cnversin (infix, pre-fix, pst-fix) Parsing Simulatin f recursin etc. Implementatin f Stack Data Structure Stack can be easily implemented using an Array r a Linked List. Arrays are quick, but are limited in size and Linked List requires verhead t allcate, link, unlink, and deallcate, but is nt limited in size. Here we will implement Stack using array.

4 Algrithm fr PUSH peratin 1. Check if the stack is full r nt. 2. If the stack is full, then print errr f verflw and exit the prgram. 3. If the stack is nt full, then increment the tp and add the element. Algrithm fr POP peratin 1. Check if the stack is empty r nt. 2. If the stack is empty, then print errr f underflw and exit the prgram. 3. If the stack is nt empty, then print the element at the tp and decrement the tp. Belw we have a simple C++ prgram implementing stack data structure while fllwing the bject riented prgramming cncepts. Psitin f Tp Status f Stack

5 -1 Stack is Empty 0 Only ne element in Stack N-1 Stack is Full N Overflw state f Stack Analysis f Stack Operatins Belw mentined are the time cmplexities fr varius peratins that can be perfrmed n the Stack data structure. Push Operatin : O(1) Pp Operatin : O(1) Tp Operatin : O(1) Search Operatin : O(n) The time cmplexities fr push() and pp() functins are O(1) because we always have t insert r remve the data frm the tp f the stack, which is a ne step prcess. Algrithm STEP 1 START STEP 2 Stre the element t push int array STEP 3 Check if tp== (MAXSIZE-1) then stack is full else gt step 4 STEP 4 Increment tp as tp = tp+1 STEP 5 Add element t the psitin stk[tp]=num STEP 6 STOP Prgram

6 1. #include <stdi.h> 2. #define MAXSIZE struct stack 5. { 6. int stk[maxsize]; 7. int tp; 8. }; 9. typedef struct stack STACK; 10. STACK s; vid push(vid); 13. vid display(vid); vid main () 16. { 17. int chice; 18. s.tp = -1; 19. d 20. { 21. push(); 22. printf ("D yu want t cntinue(type 0 r 1)?\n"); 23. scanf ("%d", &chice); 24. }while(chice==1); 25. display(); 26. } vid push () 29. {

7 30. int num; 31. if (s.tp == (MAXSIZE - 1)) 32. { 33. printf ("Stack is Full\n"); 34. return; 35. } 36. else 37. { 38. printf ("Enter the element t be pushed\n"); 39. scanf ("%d", &num); 40. s.tp = s.tp + 1; 41. s.stk[s.tp] = num; 42. } 43. return; 44. } vid display () 47. { 48. int i; 49. if (s.tp == -1) 50. { 51. printf ("Stack is empty\n"); 52. return; 53. } 54. else 55. { 56. printf ("\n The status f the stack is \n"); 57. fr (i = s.tp; i >= 0; i--) 58. {

8 59. printf ("%d\n", s.stk[i]); 60. } 61. } 62. printf ("\n"); 63. } Algrithm fr Pp STEP 1 START STEP 2 Check if tp== (-1) then stack is empty else gt step 4 STEP 3 Access the element tp is pinting num = stk[tp]; STEP 4 Decrease the tp by 1 tp = tp-1; STEP 6 STOP Prgram 1. #include <stdi.h> 2. #define MAXSIZE 5 3. struct stack 4. { 5. int stk[maxsize]; 6. int tp; 7. }; 8. typedef struct stack STACK; 9. STACK s; 10. vid push(vid); 11. vid display(vid); 12. int pp(vid); 13. vid main () 14. { 15. int chice;

9 16. s.tp = -1; 17. d 18. { 19. push(); 20. printf ("D yu want t cntinue(type 0 r 1)?\n"); 21. scanf ("%d", &chice); 22. }while(chice==1); 23. pp(); 24. display(); 25. } 26. vid push () 27. { 28. int num; 29. if (s.tp == (MAXSIZE - 1)) 30. { 31. printf ("Stack is Full\n"); 32. return; 33. } 34. else 35. { 36. printf ("Enter the element t push\n"); 37. scanf ("%d", &num); 38. s.tp = s.tp + 1; 39. s.stk[s.tp] = num; 40. } 41. return; 42. } 43. int pp () 44. {

10 45. int num; 46. if (s.tp == - 1) 47. { 48. printf ("Stack is Empty\n"); 49. return (s.tp); 50. } 51. else 52. { 53. num = s.stk[s.tp]; 54. printf ("pped element is = %dn", s.stk[s.tp]); 55. s.tp = s.tp - 1; 56. } 57. return(num); 58. } 59. vid display () 60. { 61. int i; 62. if (s.tp == -1) 63. { 64. printf ("Stack is empty\n"); 65. return; 66. } 67. else 68. { 69. printf ("\n Current stack is \n"); 70. fr (i = s.tp; i >= 0; i--) 71. { 72. printf ("%d\n", s.stk[i]); 73. }

11 74. } printf ("\n"); Evaluatin f an Infix Expressin that is Fully Parenthesized Input: (((2 * 5) - (1 * 2)) / (9-7)) Output: 4 Analysis: Five types f input characters * Opening bracket * Numbers * Operatrs * Clsing bracket * New line character Input String: (((2 * 5) - (1 * 2)) / (9-7)) Input Symbl Stack (frm bttm t tp) Operatin ( ( ( ( ( ( ( ( ( 2 ( ( ( 2 * ( ( ( 2 * 5 ( ( ( 2 * 5 ) ( ( 10 2 * 5 = 10 & Push - ( ( 10 -

12 Input Symbl Stack (frm bttm t tp) Operatin ( ( ( 10 - ( 1 ( ( 10 - ( 1 * ( ( 10 - ( 1 * 2 ( ( 10 - ( 1 * 2 ) ( ( * 2 = 2 & Push ) ( = 8 & Push / ( 8 / ( ( 8 / ( 9 ( 8 / ( 9 - ( 8 / ( 9-9 ( 8 / ( 9-7 ) ( 8 / = 2 & Push ) 4 8 / 2 = 4 & Push New line Empty Pp & Print Input String: (2 * 5-1 * 2) / (11-9) Input Symbl Character Stack (frm bttm t tp) Integer Stack (frm bttm t tp) Operatin perfrmed ( ( 2 ( 2 * ( * Push as * has higher pririty

13 Input Symbl Character Stack (frm bttm t tp) Integer Stack (frm bttm t tp) Operatin perfrmed 5 ( * ( * ( - 10 Since '-' has less pririty, we d 2 * 5 = 10 We push 10 and then push '-' 1 ( * ( - * 10 1 Push * as it has higher pririty 2 ( - * ) ( ( 8 Perfrm 1 * 2 = 2 and push it Pp - and 10-2 = 8 and push, Pp ( / / 8 ( / ( 8 11 / ( / ( / ( ) / 8 2 New line 4 Perfrm 11-9 = 2 and push it Perfrm 8 / 2 = 4 and push it

14 Input Symbl Character Stack (frm bttm t tp) Integer Stack (frm bttm t tp) Operatin perfrmed 4 Print the utput, which is 4 Evaluatin f Prefix Expressin Input String: / - * 2 5 * Input Character Stack (frm Integer Stack (frm Operatin Symbl bttm t tp) bttm t tp) perfrmed / / - / * / - * 2 / - * 2 5 / - * 2 5 * / - * 2 5 * 1 / - * 2 5 * 1 2 / - * 2 5 * / - * 2 5 * / - * 2 5 * / - * 2 5 * \n / - * 2 5 * / - * 2 5 * / - * 2 5 * = 2

15 Input Character Stack (frm Integer Stack (frm Operatin Symbl bttm t tp) bttm t tp) perfrmed / - * 2 5 * / - * 2 5 * / - * * 2 = 2 / - * / - * / * 2 = 10 / = 8 Stack is empty 4 8 / 2 = 4 Stack is empty Print 4

Data Structure Interview Questions

Data Structure Interview Questins A list f tp frequently asked Data Structure interview questins and answers are given belw. 1) What is Data Structure? Explain. Data structure is a way that specifies hw