Syllabus for B.Tech. I Year II semester Code:121CS01 DATA STRUCTURES AND C++ UNIT – IIntroduction to data structures: Abstract data type(ADT), Stacks and Queues circular queues and

their implementation with arrays. Stack applications: infix to post fix conversion, postfix expression evaluation. Applications of queues.

UNIT – IISingly linked lists, doubly linked lists, circular list and their operations, representing stacks and

queues with linked lists. UNIT – IIITrees- Binary tress, terminology, representation, traversalsGraphs- terminology, representation, graph traversals (dfs & bfs).UNIT - IVSearching - Linear and binary search methods.Sorting - Bubble sort, selection sort, Insertion sort, Quick sort, merge sort.UNIT – VIntroduction to c++ programming-object oriented programming concepts, Structured Vs OOP.Classes and objects-class definition, Objects, class scope and accessing members, Constructors-

default constructor, parameterized constructor, constructor initialization list, copy constructor. Destructors.

UNIT – VIStatic class members, this pointer, friend functions, Dynamic memory management with operators

new and delete.Overloading-function overloading, Operator overloading, restrictions on operator overloading, overloading unary and binary operators,templates, inheritance.

• Code: 121CS71 DATASTRUCTURES AND C++ LAB (Common to all Branches)

1.Write a C program that implement stack and its operations using arrays 2. Write a C program that implement Queue and its operations using arrays. 3. Write a C program that uses Stack operations to perform the following i) Converting infix expression into postfix expression

ii) Evaluating the postfix expression4. Write a C program that uses functions to perform the following operations on singly linked list.: i) Creation ii) Insertion iii) Deletion iv) Traversal 5. Write a C program that uses functions to perform the following operations on doubly linked list.: i) Creation ii) Insertion iii) Deletion iv) Traversal in both ways 6 Write a C program that uses functions to perform the following: i) Creating a Binary Tree of integers ii) Traversing the above binary tree in preorder, in order and post order.7. Write C programs that use both recursive and non recursive functions to perform the following searching operations for a Key value in a given list of integers : i) Linear search ii) Binary search8. Write C programs that implement the following sorting methods to sort a given list of integers in

ascending order: i) Bubble sort ii) Quick sort9. Write C programs that implement the following sorting methods to sort a given list of integers in

ascending order: i)Insertion sort ii) Merge sort iii) Selection Sort10. Write a C++ program that prints all real solutions to the quadratic equation ax2+bx+c=0. Read in a,b,c and use the quadratic formula. If the descremainant b2-4ac is negative, display a message stating that there are no real solutions.11. A Fibonacci Sequence is defined as follows: the first and second terms in the sequence are 0 and

Subsequent terms are found by adding the preceding two terms in the sequence. Write a C++ program to generate the first n terms of the sequence.

12. Write a C++ program that checks whether a given string is palindrome or not.

UNIT-I

Topics to be covered 1.Introduction to data structures. 2. Abstract data type (ADT) 3. Stacks and queues 4. Circular queues and their implementation with arrays. 5. Stack applications:

5.1. infix to post fix conversion 5.2. postfix expression evaluation.

6. Applications of queues

Introduction to data structuresData- it is a collection of items or valuesType- it is a collection of values. ex- integer- 0 to 9 boolean- true or falseData type- it is a data of type and together with the

set of operations used to apply on the type. ex- integer is a member of type integer and its

operations are addition, subtraction etc…

1.Introduction to data structures.

Definition:- A data structure is an arrangement of data in a computers memory or even on disk storage. It has a different way of storing and organizing (accessing) data in a computer.

Objective of data structure:- manipulation of real-life data requires the following essential tasks-

1.storage representation of user data2. Retrieval of stored data3. transformation of user data

• Mathematical definition of data structure is D=(d,f,a)

where D= data structure d= a set of variables (data objects). f= a set of functions a= set of rules to implement the

functions.

2. Abstract data type (ADT)

Data structure is implemented around the concept of an abstract data type that defines the data together with the operations.

ADT contains - data - operations - no implementation details. ADT is also called as user defined data type. Only tells about what are the data values required and what

operations performed on those objects.

Overview of data structures

Several data structures are available in the computer science and used based on their applications.

Data structures are classified into different types.

Data structure

Linear ds Non Linear ds

Arrays

Linked list stack queues

Trees

Graphs

1.Linear data structure- all the elements are stored in sequential

order or linear order means that all the elements are adjacent to each other. Each element has exactly two neighbors. Predecessor and successor.

• the first element does not have predecessor • The last element does not have successor.2. Non linear data structure- no such sequence

in elements, if one element is connected to a more than two adjacent element then it is a non linear data structure.

Applications of data structures

Implementing data bases of different organizations (ds used is B-Trees)

Implement compilers for different languages (ds used is hash tables).

Used in every program and software system.

3. Stacks and queuesDefinition - A stack is an ordered collection of

homogeneous data elements, where the insertion and deletion takes place at one end, known as TOP.

The stack is also called LAST IN FIRST OUT(LIFO) It means: the element which is inserted last must be

deleted first Example 1. No of plates in cafeteria 2. stack of coins

Stack maintains a pointer called top, which keeps track Stack maintains a pointer called top, which keeps track

of the top most element in the stack.of the top most element in the stack. Any insertions or deletions should be based upon the Any insertions or deletions should be based upon the

value of top.value of top. It works on the basis of LIFO (Last in First out).It works on the basis of LIFO (Last in First out). According to the definition, new elements are inserted According to the definition, new elements are inserted

from top and the elements are deleted from same end from top and the elements are deleted from same end i.e again top. i.e again top.

This suggests that the element inserted most recently This suggests that the element inserted most recently can only be deleted.can only be deleted.

In the stack, the elements are removed in the reverse In the stack, the elements are removed in the reverse order of that in which they were added to the stack i.e order of that in which they were added to the stack i.e last element inserted is to be deleted first.last element inserted is to be deleted first.

So it is called last in first out.So it is called last in first out. Stack has structured with two operations Stack has structured with two operations 1.1. push- insertion\ adding elements on to a stackpush- insertion\ adding elements on to a stack2.2. Pop- deletion \ removing element from the stackPop- deletion \ removing element from the stack

Basic operations:Basic operations:The basic operations are insertion, The basic operations are insertion,

deletion ,display.deletion ,display.

In stacks, special terms are given for insert In stacks, special terms are given for insert and delete. i.e push for insert and pop is for and delete. i.e push for insert and pop is for delete.delete.

Push: inserting or adding element into the Push: inserting or adding element into the stack is called push.stack is called push.

Pop: deleting or removing element from the Pop: deleting or removing element from the stack is called pop.stack is called pop.

Elements are inserted in the order as A,B,C,D,EElements are inserted in the order as A,B,C,D,EIt represents the stack of 5 elements.It represents the stack of 5 elements.

The top most element in the stack is EThe top most element in the stack is EIf we want to delete element E has to be deleted If we want to delete element E has to be deleted firstfirst

Pop operation- delete element from the stack

Example :-

ADT For Stack

ADT for stack struct stack

{ int stack[5],top;

} void push(); void pop();

void display();

Implementing stack using Implementing stack using arraysarrays

Algorithm for inserting element into the stack:Algorithm for inserting element into the stack:

Algorithm push()Algorithm push()1. if top=(SIZE-1)1. if top=(SIZE-1)then write (‘stack overflow’)then write (‘stack overflow’) else else 2. read item or data 2. read item or data 3. top3. top←top+1←top+14. stack[top]← item4. stack[top]← item5. stop5. stop

Explanation:Explanation: The stack is of size max. This procedure inserts an element The stack is of size max. This procedure inserts an element

item on to the top of a stack which is represented by an item on to the top of a stack which is represented by an array stack.array stack.

The first step of this algorithm checks for an overflow The first step of this algorithm checks for an overflow condition.condition.

Overflow means inserting element into a stack which is Overflow means inserting element into a stack which is full.full.

If the top value reaches to maximum size of the stack then If the top value reaches to maximum size of the stack then elements cannot be inserted into the stack i.e. stack is full.elements cannot be inserted into the stack i.e. stack is full.

Otherwise top is incremented by one and element is Otherwise top is incremented by one and element is inserted into the stack.inserted into the stack.

Algorithm to delete elements from the stack:Algorithm to delete elements from the stack:

Algorithm pop()Algorithm pop()1. if top=-11. if top=-1then write (‘stack underflow’)then write (‘stack underflow’)

elseelse 2. item 2. item ← stack[top]← stack[top]3. top ← top-13. top ← top-1

Explanation:Explanation:This procedure deletes an element from the stack.This procedure deletes an element from the stack.

The first step of this algorithm checks for The first step of this algorithm checks for underflow condition.underflow condition.

If the top value is -1 then stack is empty.If the top value is -1 then stack is empty.

Empty stack is known as underflow.Empty stack is known as underflow.

Takeout the element from the location where, the Takeout the element from the location where, the top is pointing and then decrement top by one.top is pointing and then decrement top by one.

Display of stack:Display of stack:Printing the contents of stack after push and pop Printing the contents of stack after push and pop

operations.operations.Algorithm print()Algorithm print()1. if top=-11. if top=-1then write (‘stack empty’)then write (‘stack empty’) 2. Repeat for i 2. Repeat for i ← top to 0← top to 0print(stack[i])print(stack[i])3. stop3. stop

A queue is a linear data structure in which insertion take place from A queue is a linear data structure in which insertion take place from one end called one end called rear endrear end and deletions take place from other end and deletions take place from other end called called front endfront end i.e insertion and deletion take place from different i.e insertion and deletion take place from different ends.ends.

The principle used to in queue is The principle used to in queue is FIFO.(First In First Out)FIFO.(First In First Out) FIFOFIFO- the element which is inserted First must be deleted First.- the element which is inserted First must be deleted First. In a queue there are two variables one is the In a queue there are two variables one is the rearrear and other one is and other one is

frontfront.. the element must be always the element must be always added at rearadded at rear end and end and removed from removed from

the frontthe front. . Basic operations on queue:Basic operations on queue:The operations that can be performed on queue areThe operations that can be performed on queue are Insertion\ EnqueueInsertion\ Enqueue Deletion\ DequeueDeletion\ Dequeue DisplayDisplay

QueuesQueues

Front rear

Bus Stop Queue

Bus Stop

frontrear

rear rear rear rear

Bus Stop Queue

Bus Stop

frontrear

rear rear

Bus Stop Queue

Bus Stop

frontrear

rear

Bus Stop Queue

Bus Stop

frontrear

rear

FrontRear

FrontRear

FrontRear

•A queue is like a line of people waiting forA queue is like a line of people waiting for• a bank teller. The queue has a a bank teller. The queue has a frontfront and a and a rearrear..

New people must enter the queue at the rear.New people must enter the queue at the rear.

When an item is taken from the queue, it always comes from the front.When an item is taken from the queue, it always comes from the front.

• Different types of queues1. Linear queue or queue2. Circular queue3. Doubly ended queue( dequeue)4. Priority queue

This type of data structure is used in time This type of data structure is used in time sharing systems where many user jobs sharing systems where many user jobs will be waiting in the system queue for will be waiting in the system queue for processing. These jobs may request the processing. These jobs may request the services of CPU, main memory or external services of CPU, main memory or external devices such as printer.devices such as printer.

Working of a linear queue:-

i) Initially front=rear= -1. It indicates queue is empty.0 1 2 3 4

front=rear=-1

0 1 2 3 4

ii) Add 10

10

front rear

0 2 3 4

iii) Add 20

front rear

1

10 20

0 2 3 4

iv) Add 30

front rear

110 20 30

0 2 3 4

v) Add 40

front rear

110 20 30 40

0 2 3 4

vi) Add 50

front rear

110 20 30 40 50

0 2 3 4

vii) Add 60 (overflow)

front rear

1

10 20 30 40 50

0 2 3 4

viii) delete (10 is removed)

front rear

1

20 30 40 500

front rear

1

30 40 50

ix) delete (20 is removed) 2 3 4

0

front rear

1

40 50

x) delete (30 is removed)

2 3 4 0

front rear

1

50

xi) delete (40 is removed) 2 3 4

0

front=rear=-1

1

ix) delete (underflow)

2 3 40

front=rear=-1

1

xii) delete (50 is removed)

2 3 4

Implementation of queue using Implementation of queue using arrayarray

Algorithm insert( )Algorithm insert( )1.1. If rear If rear ≥ ≥ size-1size-1

then write (‘overflow’)then write (‘overflow’)2.2. Read itemRead item3.3. rearrear←← rear + 1 rear + 14.4. queue[rear]queue[rear]←← item item5.5. If(front==-1)If(front==-1)6.6. front++;front++;7.7. stopstop

Explanation:Explanation:This procedure adds an element item to the This procedure adds an element item to the queue.queue.First it checks for an overflow condition.First it checks for an overflow condition.If the rear value reaches or exceeds size of the If the rear value reaches or exceeds size of the queue queue then elements cannot be inserted into the queue.then elements cannot be inserted into the queue. ie. Overflow.ie. Overflow.Whenever element is inserted into the queue,Whenever element is inserted into the queue, rear is increment by onerear is increment by one and place the element in the location and place the element in the location where rear is pointing.where rear is pointing.

Algorithm to delete element from the Algorithm to delete element from the queuequeue

Algorithm delete()Algorithm delete()1.1. If (front= = -1)or (front> rear)If (front= = -1)or (front> rear)

then write (‘queue underflow’)then write (‘queue underflow’)item item ←← queue [front] queue [front]2. front 2. front ←← front + 1 front + 1Explanation:Explanation:This procedure deletes an element from the queue.This procedure deletes an element from the queue.The first step of this algorithm checks for underflow condition.The first step of this algorithm checks for underflow condition.If the front value is -1or greater than rear then queue is empty.If the front value is -1or greater than rear then queue is empty.Take out the element from the location where, the front is pointing andTake out the element from the location where, the front is pointing and store it in the variable, then increment front by one. store it in the variable, then increment front by one.

Algorithm to display elements in a queueAlgorithm to display elements in a queue

1.1. if((front==-1)||(front>rear))if((front==-1)||(front>rear)) 1.1 print statck is Underflow1.1 print statck is Underflow2. Else2. Else 2.1 repeat for i->front to rear2.1 repeat for i->front to rear 2.2. print queue[i];2.2. print queue[i];

Drawback in queueIn a queue when the rear pointer reaches to the end of the queue, insertion would be denied even if room is available at the front one way to remove this is using the circular queue

Program: implementation of queue using array# include <stdio.h># define size 4void insertion();void deletion();void display();int front=-1,rear=-1,item,choice,queue[size];void main(){clrscr();while(1){printf("\n*** MENU ***\n 1. INSERTION\n 2. DELETION\n 3.TRAVERSE\n 4. EXIT\n");printf("enter your choice:");scanf("%d",&choice);switch(choice){case 1:insertion();break;case 2:deletion();break;case 3:display();break;case 4:exit();default:printf("*** wrong choice ***\n");}}}

void insertion(){if(rear>=size-1)printf("*** queue is full ***\n");else{printf("enter item into queue:");scanf("%d",&item);rear++;queue[rear]=item;if(front==-1)front++;} }

void deletion(){if((front==-1)||(front>rear))printf("*** queue is empty ***\n");else{item=queue[front];front++;printf("the deleted item from queue is %d\n",item);}}void display(){

int i;if((front==-1)||(front>rear))printf("*** queue is empty ***\n");else{printf("\n elements in queue:- ");for(i=front;i<=rear;i++)printf("%d ",queue[i]);}}

EMPTY QUEUE

Circular queuesQ[0] Q[1] Q[2] Q[3] Q[N]

Delete element 5

rear

• How to test whether circular queue is empty or full?• The circular q is controlled by the MOD operation.• Circular queue is empty when front =-1 rear=-1Circular queue is full front = (rear+1)% SIZE

Implementation of circular queue using array

• Algorithm for insertion1.if((front == 0 && rear == SIZE-1) || (front == (rear+1)%size) 2.printf("Queue Overflow \n");return;3.if (front == -1) /*If queue is empty */ 3.1 front = 0; 3.2 rear = 0;4.else 5.if(rear == SIZE-1)/*rear is at last position of queue */ 6.rear = 0;7. else8.rear = rear+1;9.Read item10.cq[rear] = item ;11.end

• Algorithm for deletion• 1.if (front == -1) 2.printf("Queue Underflow\n") return 3.if(front == rear) /* queue has only one element */ 3.1front = -1; 3.2rear=-1;

4.else 5.if(front == SIZE-1)• front = 0; 6.else 7.front = front+1; 8.Stop

int insert(){int item;if((front == 0 && rear == SIZE-1) || (front == rear+1)){printf("Queue Overflow \n");return;}if (front == -1) /*If queue is empty */{front = 0;rear = 0;}elseif(rear == SIZE-1)/*rear is at last position of queue */rear = 0;elserear = rear+1;printf("Input the element for insertion in queue : ");scanf("%d", &item);cq[rear] = item ;printf("the element %d at %d position and front=%d,rear=%d\n",cq[rear],rear,front,rear);return;}/*End of insert()*/

int del(){if (front == -1){printf("Queue Underflow\n");return ;}printf("Element deleted from queue is : %d\n",cq[front]);if(front == rear) /* queue has only one element */{front = -1;rear=-1;}elseif(front == SIZE-1)front = 0;elsefront = front+1;printf("front=%d,rear=%d\n",front,rear);return;}/*End of del() */

Deletion

display() int display(){int front_pos = front,rear_pos = rear;if(front == -1){printf("Queue is empty\n");Return;}printf("Queue elements :\n");if( front_pos <= rear_pos )while(front_pos <= rear_pos){printf("%d ",cq[front_pos]);front_pos++;}else{while(front_pos <= SIZE-1){printf("%d ",cq[front_pos]);front_pos++;}front_pos = 0;while(front_pos <= rear_pos){printf("%d ",cq[front_pos]);front_pos++;}}/*End of else */printf("\n");return;}/*End of display() */

Applications of queuesThere are several applications of queues in computer science.1. Implement various aspects of operating systems.2. CPU scheduling in Multiprogramming environment- single CPU

has to serve more than one program simultaneously.3. Round Robin CPU scheduling algorithm.4. In operating System maintains a queue of processes that are

ready to process or that are waiting for particular event to occur.5. Computer system maintains a buffer and is implemented as a

queue.6. Printer7. Call waiting when you are attending other call

8. a file server in a computer network handles file access request from many clients throughout the network. Servers have a limited capacity to service request from clients. when that capacity is exceeded, client requests wait in queues

9. This type of data structure is used in time sharing systems where 9. This type of data structure is used in time sharing systems where many user jobs will be waiting in the system queue for many user jobs will be waiting in the system queue for processing. These jobs may request the services of CPU, main processing. These jobs may request the services of CPU, main memory or external devices such as printer.memory or external devices such as printer.

Circular queue using array# include<stdio.h>#include<stdlib.h># define SIZE 4int insert();int del();int display();int cq[SIZE];int front = -1;int rear = -1;main(){while(1){printf("1.Insert\n");printf("2.Delete\n");printf("3.Display\n");printf("4.Quit\n");printf("Enter your choice : ");scanf("%d",&choice);

switch(choice){case 1 :

insert();break;

case 2 :del();break;

case 3:display();break;

case 4:exit(0);

default:printf("Wrong choice\n");

}/*End of switch*/}/*End of while */}/*End of main()*/

int insert(){int item;if((front == 0 && rear == SIZE-1) || (front == rear+1)){printf("Queue Overflow \n");return;}if (front == -1) /*If queue is empty */{front = 0;rear = 0;}elseif(rear == SIZE-1)/*rear is at last position of queue */rear = 0;elserear = rear+1;printf("Input the element for insertion in queue : ");scanf("%d", &item);cq[rear] = item ;printf("the element %d at %d position and front=%d,rear=%d\n",cq[rear],rear,front,rear);return;}/*End of insert()*/

example1.encq(A)2.encq(B)3.encq(c )4. Encq ( D )5.Decq6.encq(E)7. Decq8.encq( F)9.Decq10. Decq11.Decq12. Decq

Applications of stacksApplications of stacksParenthesis matching.Parenthesis matching.Evaluation of postfix expressions.Evaluation of postfix expressions. Infix to prefix conversions.Infix to prefix conversions. Infix to postfix conversions.Infix to postfix conversions.Recursion.Recursion.Quick sort.Quick sort.

1.Parenthesis matching1.Parenthesis matching

The objective of this function is to check the matching of The objective of this function is to check the matching of parenthesis in an expression parenthesis in an expression

i.ei.e In an expression the no of left parenthesis must be equal to In an expression the no of left parenthesis must be equal to

no: of right parenthesis.no: of right parenthesis.

Ex:Ex: ((A+B)*C)((A+B)*C)This is a valid expression because in this no of left This is a valid expression because in this no of left

parenthesis (2) = no: of right parenthesis (2).parenthesis (2) = no: of right parenthesis (2).

Conversion of expressionsConversion of expressionsArithmetic expressions can be represented in three ways:Arithmetic expressions can be represented in three ways: Infix notationInfix notation Prefix notationPrefix notation Postfix notationPostfix notation1. Infix notation- In which operator should be placed in between the two operands.Example- A+B C-D E*F G/H.2. Prefix notation (polish notation)- • Operator preceded by the operand is called prefix notation Examples +AB -CD *EF \GH.3. Postfix notation(reverse polish notation or suffix notation)-

• Operator should be placed after operands. AB+ CD- EF* GH\

Notations – Conversions

Consider the infix expression: 2 + 3 * (5 – 7) / 9

Let us insert implicit parentheses(2 + ((3 * (5 – 7)) / 9))

Transfer the operators to the beginning of parentheses(+ 2 (/ (* 3 (– 5 7)) 9))

Remove the parentheses: + 2 / * 3 – 5 7 9This is the equivalent prefix expression.

Transfer the operators to the end of parentheses(2 ((3 (5 7 –) *) 9 /) +)

Remove the parentheses: 2 3 5 7 – * 9 / +This is the equivalent postfix expression.

ExamplesInfix

ExpressionPrefix

ExpressionPostfix

Expression

2 + 3 + 2 3 2 3 +

2 + 3 * 5 + 2 * 3 5 2 3 5 * +

(2 + 3) * 5 * + 2 3 5 2 3 + 5 *

2 * 3 – (5 + 9) – * 2 3 + 5 9

2 3 * 5 9 + –

Infix to post fix(RPN) ConversionAlgorithm to convert infix expression to RPN:1. Declare a stack.2. Repeat the following steps until the end of the infix expression is reached.

1. Get input token (constant, variable, arithmetic operator, left parenthesis, right parenthesis) in the infix expression.

2. If the token is1. A left parenthesis: Push it onto the stack.2. A right parenthesis:

1. Pop and display stack elements until a left parenthesis is on the top of the stack.

2. Pop the left parenthesis also, but do not display it.3. An operator:

1. While the stack is nonempty and token has lower or equal priority than stack top element, pop and display.

2. Push token onto the stack.4. An operand: Display it.

3. When the end of the infix expression is reached, pop and display stack items until the stack is empty.(Note: Left parenthesis in the stack has lowest priority)

Note • 1. the lower precedence operator

never placed on top of the higher precedence.

Operator Precedence

Infix expression- (A+B)^C-(D*E)/F

Infix Stack Post fix

( ( Empty

A ( A

+ (+ A

B (+ AB

) Empty AB+

^ ^ AB+

C ^ AB+C

- - AB+C^

( -( AB+C^

D -( AB+C^D

* -(* AB+C^D

E -(* AB+C^DE

) - AB+C^DE*

/ -/ AB+C^DE*

F -/ AB+C^DE*F

Empty AB+C^DE*F/-

Postfix (reverse polish notation) expression evaluation

• Algorithm1.Scan expression from left to right and repeat steps 2 and 3 for each

element of expression.2. If an operand is encountered, put it on stack.3.If an operator op1 is encountered then 3.1 remove the top two elements of stack, where A is the top and B is

the next top element. 3.2 evaluate B op1 A 3.3 push the result back on to the stack.4. set the top value on stack.5. stop

Evaluate the expression• Postfix:- 5,6,2,+,*,12,4,/,-

Symbol scanned stack content 5 5

6 5 6

2 5 6 2

+ 5 8

* 40

12 40 12

4 40 12 4/ 40 3

Convert infix to postfix expression1. (A-B)*(D/E)2. (A+B^D)/(E-F)+G3. A*(B+D)/E-F*(G+H/K)4. ((A+B)*D)^(E-F)5. (A-B)/((D+E)*F)6. ((A+B)/D)^((E-F)*G)7. 12/(7-3)+2*(1+5)8. 5+3^2-8/4*3+69. 6+2^3+9/3-4*510. 6+2^3^2-4*5Evaluate the postfix expression1. 5,3,+,2,*,6,9,7,-,/,-2. 3,5,+,6,4,-,*,4,1,-,2,^,+3. 3,1,+,2,^7,4,1,-,2,*,+,5.-

#include<stdio.h>#include<ctype.h>#include<string.h> int priority(char c); int push(char c); int pop(); static char str[30];int top=-1;void main(){char in[30],post[30],ch;int i,j,l;printf("enter the string");gets(in);l=strlen(in);

Write a C program to convert infix to postfix evaluation

for(i=0,j=0;i<l;i++){if(isalpha(in[i]))post[j++]=in[i];else{if(in[i]=='(')push(in[i]);else if(in[i]==')')while((ch=pop())!='(')post[j++]=ch;else{while(priority(in[i])<=priority(str[top]))post[j++]=pop();push(in[i]);}}}while(top!=-1)post[j++]=pop();post[j]='\0';printf("\n equivalent infix to postfix is:%s",post);

}

int priority (char c){switch(c){case'+':case'-': return 1;case'*':case'/':return 2;case'$':return 3;case '^':return 4;}return 0;}int push(char c){str[++top]=c;}

pop(){return(str[top--]);}