Program that convert Infix expression into Post fix expression in C language.

 

#include<stdio.h>
#include<ctype.h>
#include<conio.h>
char stack[100];
int top = -1;

void push(char x)
{

top=top+1;
stack[top] = x;

}

char pop()
{

if(top == -1)
return -1;
else
{

int n=stack[top];

top=top-1;

return n;

}

}

int priority(char x)
{

if(x == '(')
return 0;
if(x == '+' || x == '-')
return 1;
if(x == '*' || x == '/')
return 2;
return 0;

}

void main()
{

char exp[100];
char *e, x;
printf("Enter the expression : ");
scanf("%s",exp);
printf("\n");
e = exp;

while(*e != '\0')
{

if(isalnum(*e))
printf("%c ",*e);
else if(*e == '(')
push(*e);
else if(*e == ')')

{
while((x = pop()) != '(')

printf("%c ", x);

}
else
{

while(priority(stack[top]) >= priority(*e))
printf("%c ",pop());
push(*e);

}
e++;
}

while(top != -1)
{

printf("%c ",pop());

}
getch();
}