infixtopostfix.c

#include<stdio.h>
#include<ctype.h>

char stack[100];
int top=-1;
void push(char x)
{
stack[++top]=x;
}



char pop()
{
if(top==-1)
return -1;
else 
return stack[top--];
}



int priority(char x)
{
if(x=='(')
return 0;
if (x=='+'||x=='-')
return 1;
if(x=='*'||x=='/')
return 2;
return 0;
}




int main()
{
char expo[100];
char *e,x;
printf("\nEnter the expression");
scanf("%s",expo);
printf("\n");
e=expo;
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());
return 0;
}