DSA C25 Program

Group C: (Assignment No: 02) (SPPU Syllabus Assignment No: 25)
Problem Statement:

Implement C++ program for expression conversion as infix to postfix and its evaluation using stack based on given conditions
i. Operands and operator, both must be single character.
ii. Input Postfix expression must be in a desired format.
iii. Only '+', '-', '*' and '/ ' operators are expected.

Program Code:

//================================================================================================================================
// Name        : infix_postfix.cpp
// Author      : Nitin Shivale
// Version     : 1
// Copyright   : Your copyright notice
// Description : Conversion of infix expression to postfix expression and evaluation of postfix expression using stack, Ansi-style
//================================================================================================================================

#include <iostream>
#include<ctype.h>
using namespace std;
//class inpo containing data member and member functions
class inpo
{
    char in[20],po[20],stk[10];//stack for expression conversion.
    int i,j,is,ic,top,top1; //Two top one for stack and one for stack 1.
    int stk1[10]; //Stack 1 for expression evaluation.
public:
    inpo()
    {
     i=j=is=ic=0; //initialization of data members
     top=top1=-1;
    }
    bool IsOperand(char C)
    {
        if(C >= '0' && C <= '9') return true;
        if(C >= 'a' && C <= 'z') return true;
        if(C >= 'A' && C <= 'Z') return true;
        return false;
    }
    void getinfix() //Accept the infix expression
    {
        cout<<"\nEnter valid infix Expression: ";
        cin>>in; //Stored infix exp in in[]char array.
    }
    void showinfix() //Show the infix expression
    {
        cout<<"\t"<<in;
    }
    int isempty() //Stack basic functions.
    {
        if(top==-1)
            return 1;
        else
            return 0;
    }
    int isfull()
    {
        if(top==9)
            return 1;
        else
            return 0;
    }
    void push1(int x1)//for integer stack
    {
        top=top+1;
        stk1[top]=x1;
    }
    int pop1() //for integer stack
    {
       int s1;
       s1=stk1[top];
       top=top-1;
       return s1;
    }
    void push(char x)//for character stack
    {
        top=top+1;
        stk[top]=x;
    }
    char pop()//for character stack
    {
        char s;
        s=stk[top];
        top=top-1;
        return s;
    }
    void showpostfix()
    {
        cout<<"\t"<<po;
    }
    void convert();
    int instackprio();
    int incomingprio(char); //member functions
    void postfixExpEval();
};
void inpo::postfixExpEval() //To evaluate the postfix expression
{
    i=0;
    char ch;
    int op1,op2,res,tot;
        while(po[i]!='\0')//read postfix expression one by one
        {
            ch=po[i];
            if((ch=='+')||(ch=='-')||(ch=='*')||(ch=='/')||(ch=='^')) //isdigit(ch) built in function to check digit.
            {
                switch(ch)//if operator pop and perform operation and push back into the stack.
                {
                case '+':op2=pop1();
                         op1=pop1();
                         res=op1+op2;
                         push1(res);
                         break;
                case '-':op2=pop1();
                         op1=pop1();
                         res=op1-op2;
                         push1(res);
                         break;
                case '*':op2=pop1();
                         op1=pop1();
                         res=op1*op2;
                         push1(res);
                         break;
                case '/':op2=pop1();
                         op1=pop1();
                         res=op1/op2;
                         push1(res);
                         break;
                case '^':op2=pop1();
                         op1=pop1();
                         res=op1;
                         while(op2>1)
                         {
                          res=res*op1;
                          op2--;
                         }
                         push1(res);
                         break;
                }//end of switch

            } //end of if
            else if(IsOperand(ch))//To check operand we use IsOperand function.
            {
                push1(ch-'0'); //if operand push it inside stack
            } //end of else
            i=i+1;
        }//end of while

    tot=pop1(); //final evaluated result at the top of stack.
    cout<<"\nResult is:"<<tot;
}//end of fun

/*******************************************************************
 * Function Name: To convert infix expression to postfix expression.
 * return type: Void
 *******************************************************************/

void inpo::convert()
{
    i=j=0;
    char p,k;
    while(in[i]!='\0')//do until null character not found
    {
     p=in[i];//to read one by one from infix expression
     if((p=='(')||(p=='+')||(p=='-')||(p=='*')||(p=='/')||(p=='^')||(p==')'))
     {
         if(isempty()) //here we are dealing with operator only as per their priority.
         {
             push(p); //if initially stack is empty push
         }
         else if(p==')') //when we encountered with ')' bracket pop from stack until we r not encountered with '(' bracket.
         {
             k=pop();
             while(k!='(') //check the pop element with '(' bracket. if equal stop poping.
             {
                 po[j]=k; //pop and store it inside the postfix expression array po[].
                 j++;     //increment po[] array index by 1.
                 k=pop(); //pop next element
             }
         }
         else
         {
             is=instackprio(); //when we are pushing the operator inside the stack.
             ic=incomingprio(p);// we are always checking their incoming and instack priority.
             if(is>ic)//if instack priority is gretter than incoming priority
             {
              k=pop(); //pop the stack top operator whose priority is bigger than incoming operator from stack.
              po[j]=k;//store it in postfix expression array po[j]
              j++;  //increment j by one.
              push(p);//then push the incoming operator in stack.
             }
             else
             {
                 push(p); //if incoming operator priority is gretter than instack operator priority then
             }            // directly push the incoming operator inside the stack.
         }
     }
     else// if opearnd is their directly store it inside the postfix expression array po[j].
     {
        po[j]=p;
        j++; //increment j by one.
     }
     i=i+1; //read the next character of infix expression for conversion.
    }//end of while loop
    if(in[i]=='\0')//if we encountered with NULL Character of infix expression then
    {
        while(!isempty())//pop the stack containts until stack is not empty and
        {
         k=pop(); //pop from stack
         po[j]=k; //store it inside the postfix expression array po[j].
         j++;  //increment j by one.
        }
    }
 po[j]='\0'; // at the end of the postfix expression store null character to indicate end of the expression.
}

/* * Function to check the instack priority of operator * */
int inpo::instackprio()
{
    char b;
    b=stk[top];
    switch(b)
    {
     case '(':return 0; break;
     case '+':return 2; break;
     case '-':return 2; break;
     case '*':return 4; break;
     case '/':return 4; break;
     case '^':return 5; break;
    }
}
/* * Function to check the priority of incoming operator * */
int inpo::incomingprio(char ch)
{
    switch(ch)
    {
     case '(':return 9; break;
     case '+':return 1; break;
     case '-':return 1; break;
     case '*':return 3; break;
     case '/':return 3; break;
     case '^':return 6; break;
    }
}

int main()
{
    inpo p1;
    p1.getinfix();
    p1.showinfix();
    cout<<"\nAfter conversion from infix to postfix...\n";
    p1.convert();
    p1.showpostfix();
    cout << "\n\n!!!POSTFIX EXPRESSION EVALUATION ARE AS FOLLOWS..!!!" << endl;
    p1.postfixExpEval();
    return 0;
}

/************** OUTPUT***********************************************************
 *
 Enter valid infix Expression: 2^4
    2^4
After conversion from infix to postfix...
    24^

!!!POSTFIX EXPRESSION EVALUATION ARE AS FOLLOWS..!!!

Result is:16

Enter valid infix Expression: (9-1)/(4-2)^2
    (9-1)/(4-2)^2
After conversion from infix to postfix...
    91-42-2^/

!!!POSTFIX EXPRESSION EVALUATION ARE AS FOLLOWS..!!!

Result is:2

[student@localhost SE_Comp_A]$ g++ conv_in_po_eval.cpp
[student@localhost SE_Comp_A]$ ./a.out

Enter valid infix Expression: (8*6)/(4-2)^3
    (8*6)/(4-2)^3
After conversion from infix to postfix...
    86*42-3^/

!!!POSTFIX EXPRESSION EVALUATION ARE AS FOLLOWS..!!!

Result is:6

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Need of Data Structures

Need of  Data Structures

Data Structure is a way of representing and organizing data in such a way that we can perform operations on data effectively. Data Structures is about representation of  data elements in association, for better organization and storage.

For example, we have data student’s name "ABC" and Roll No 25. Here "ABC" is of character data type and 25 is of integer data type.

We can organize this data as a record of student. Now we can collect and store Students records in a file or database as a data structure. For example: "DEF" 34, "XYZ" 43, "HIJ" 70.

Data Structures are structures programmed to store ordered data, so that various operations can be performed on it easily. It represents the how the data is to be organized in memory. It is designed and implemented in such a way that it reduces the complexity of performing operations and increases the efficiency and result.

Basic types of Data Structures

Data structure like Integer, Float, Boolean, Char etc, are storing data. They are known as Primitive Data Structures, which store similar kind of data together.

Then to combine these different Data Structures together to perform operation or to maintain as a record we also have some complex data structures, which are used to store large and connected data which are called as Abstract Data Structure are :

·         Array

·         Stack

·         Queue

·         Linked List

·         Trees

·         Graph

All these data structures allow us to perform different operations on data. We select these data structures based on which type of operation is required. 

The data structures can also be classified on the basis of the following characteristics:

Characterstic	Description
Linear/ Sequential	In this the data items are arranged in a linear/ sequential Manner . Like Array Ex. A[10] = { 1,2,3.4,5,6,7,8,9,10}
Non-Linear	In this the data items are not in sequence. Like Tree, Graph
Homogeneous	In this all the elements are of same type. Like: Array Ex. int A[10] = { 1,2,3.4,5,6,7,8,9,10} all are of type integer        char B[10] = {a, b,c,d,e,f,g,h,i, k} all are of type character
Non-Homogeneous	In this the elements may be same or it may have different data type. Like Structures Structure student {     int roll_no;     char name[10];  }
Static	Static data structures are those whose sizes and structures associated memory locations are fixed, at compile time.  Example: Array a[10] = { 1,2,3.4,5,6,7,8,9,10} 1 2 3 4 5 6 7 8 9 10 100 102 104 106 108 110 112 114 116 118 Memory blocks will get occupied for array like this in a sequential manner at a one place. As integer will occupy 12 bytes to store the data. The next line indicates the addresses where it is allocated.
Dynamic	Dynamic structures are those which create data structure dynamically means run time. As it is getting the memory at run time for the data structure it will be in random order . Example: Linked List created using pointers