This is the pseudo code. Create a function that takes an infix expression as input and converts it to a postfix expression. It should
take pointers to two strings as input; one containing the infix expression, and second to which this
function will write the postfix expression i.e. the declaration should be
void infixToPostfix(char *infix, char *postfix, int str_size);
The algorithm is as follows:
Iterate over the infix expression’s string. For each character c,
• If c is an operand, concatenate it with the postfix expression.
• If c is an operator, check if top of stack, say m, is an operator. If so, check if the operator
precedence of m is higher or equal to the operator precedence of c; if yes, concatenate m with
postfix expression, and pop it from the stack. Keep doing this until the top of stack is not an
operator with operator precedence higher or equal to the operator precedence of c. Then push
c on the stack.
• After completely processing input expression, TopAndPop remaining operators from stack and
concatenate each with postfix expression, in the order they are popped.
You can perform string concatenation using strcat().
Answered by:- vikas_jk
Brackets other than "(" are all invalid in infix to postfix conversion, continue with your conversion as shown in the below article
Infix to postfix conversion program in C using stack (With algorithm)
here is the C code for conversion from infix to postfix
#include <stdio.h>
#include <ctype.h>
#define SIZE 50
char stack[SIZE];
int top=-1; /* Global declarations */
push(char elem)
{ /* Function for PUSH operation */
stack[++top]=elem;
}
char pop()
{ /* Function for POP operation */
return(stack[top--]);
}
int pr(char symbol)
{ /* Function for precedence */
if(symbol == '^')/* exponent operator, highest precedence*/
{
return(3);
}
else if(symbol == '*' || symbol == '/')
{
return(2);
}
else if(symbol == '+' || symbol == '-') /* lowest precedence */
{
return(1);
}
else
{
return(0);
}
}
/* Main Program */
void main()
{
char infix[50],postfix[50],ch,elem;
int i=0,k=0;
printf("Enter Infix Expression : ");
scanf("%s",infix);
push('#');
while( (ch=infix[i++]) != '\0')
{
if( ch == '(') push(ch);
else
if(isalnum(ch)) postfix[k++]=ch;
else
if( ch == ')')
{
while( stack[top] != '(')
postfix[k++]=pop();
elem=pop(); /* Remove ( */
}
else
{ /* Operator */
while( pr(stack[top]) >= pr(ch) )
postfix[k++]=pop();
push(ch);
}
}
while( stack[top] != '#') /* Pop from stack till empty */
postfix[k++]=pop();
postfix[k]='\0'; /* Make postfix as valid string */
printf("\nPostfix Expression = %s\n",postfix);
}You will have to modify function name, as your questions description suggests.
If the above doesn't help you can also https://gist.github.com/AdiPat/6a4c38dadf71a756146671757b7e3882
You can see it is mentione in the above link that "(A+B+(C+D)) is valid. {A+B+(C+D)} is invalid."
Subscribe to our weekly Newsletter & Keep getting latest article/questions in your inbox weekly
Buy us a coffee
Become a Patron