Best C Programming code for converting Infix Expression into Postfix Expression (January,2021)
Best C Programming code for converting Infix Expression into Postfix Expression
Introduction
In Data Structure one of the most important topic is Stack. Using this concept we can perform conversion of Infix expression into Postfix expression.
What is Infix Expression?
In an equation or expression when operator is in between two operands, then this type of expression/equation is Infix Expression. e.g. (a+b), here as you can see ‘+’ operator is in between two operands ‘a’ and ‘b’.
What is Postfix Expression?
In an equation or expression when operators are just after operands, then this type of expression/equation is Postfix Expression. e.g. (ab+), here as you can see operator ‘+’ is after two operands ‘a’ and ‘b’.
In this code we will convert an Infix expression into Postfix expression. i.e. (a+b) is going to convert into (ab+). Please keep one important point in mind, in this code you can take single digit operand as input. i.e. (1+2)*(3+4)
Hope you will understand the code easily. If you are finding any difficulties please feel free to comment or send me email. My email id : creativeresource2020@gmail.com.
//Program code for converting Infix expression into Postfix expression
#include<stdio.h>
#define MAX 100
typedef struct stack
{
char data[MAX];
int top;
}stack;
int getpriority(char);
int isempty(stack *);
int isfull(stack *);
char pop(stack *);
void push(stack *,char);
char peek(stack *);
void intopost(char [],char []);
void main()
{
char str[50],str1[50];
printf("Enter the infix expression: ");
gets(str);
intopost(str,str1);
printf("Post fix expression is : ");
puts(str1);
}
// Following function is converting infix into postfix notation
void intopost(char str[],char str1[])
{
stack s;
char x;
int i,j;
s.top=-1;
i=j=0;
while(str[i]!='\0')
{
if(isalnum(str[i]))
str1[j++]=str[i];
else
if(str[i] == '(')
push(&s,'(');
else
{
if(str[i] == ')')
while((x=pop(&s))!='(')
str1[j++]=x;
else
{
while(getpriority(str[i])<=getpriority(peek(&s)) && !isempty(&s))
{
x=pop(&s);
str1[j++]=x;
}
push(&s,str[i]);
}
}
i++;
}
while(!isempty(&s))
{
x=pop(&s);
str1[j++]=x;
}
str1[j]='\0';
}
//following function is returning the priority of the operator
int getpriority(char x)
{
if(x == '(')
return(0);
if(x == '+' || x == '-')
return(1);
if(x == '*' || x == '/' || x == '%')
return(2);
return(3);
}
//following function checking whether the stack is empty or not
int isempty(stack *s)
{
if(s->top==-1)
return(1);
else
return(0);
}
//following function is checking whether the stack is full or not
int isfull(stack *s)
{
if(s->top==MAX-1)
return(1);
else
return(0);
}
//following function is inserting value into the stack
void push(stack *s,char x)
{
s->top=s->top+1;
s->data[s->top]=x;
}
//following function is extracting one value at a time from the stack
char pop(stack *s)
{
int x;
x=s->data[s->top];
s->top=s->top-1;
return(x);
}
//following function is returning the top most value in the stack
char peek(stack * s)
{
return(s->data[s->top]);
}