#include
#include
#include
#include
#include
int f(char);
int r(char);
void push(char);
char pop(void);
char s[20];
int top=-1;
void main()
{
int rank=0,i=0,j=0;
char next,c,infix[20],polish[20],temp;
clrscr();
gets(infix);
push('#');
strcpy(polish,NULL);
next=infix[i];
while(next!='#')
{
while(f(next)<=f(s[top]))
{
temp=pop();
polish[j]=temp;
j++;
rank=rank+r(temp);
if(rank<1)
{
printf(" I N V A L I D ");
getch();
exit(0);
}
}
push(next);
i++;
next=infix[i];
}
while(s[top]!='#')
{
temp=pop();
polish[j]=temp;
j++;
rank=rank+r(temp);
if(rank<1)
{
printf(" I N V A L I D ");
getch();
exit(0);
}
}
if(rank==1)
{
printf(" V A L I D ");
puts(polish);
//getch();
}
else
{
printf("I N V A L I D");
exit(0);
getch();
}
getch();
}
// 4 f
int f(char c)
{
if(c=='+'|| c=='-')
return (1);
else if(c=='*'|| c=='/')
return (2);
else if(isalpha(c))
return (3);
else if(c=='#')
return (0);
}
// 4 rank
int r(char c)
{
if(c=='+'||c=='-'||c=='*'||c=='/')
return (-1);
else
return (1);
}
// 4 push
void push(char c)
{
top=top+1;
s[top]=c;
return(s[top]);
}
// 4 pop
char pop(void)
{
top=top-1;
return(s[top+1]);
}
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| Author: m v lathkar | Member Level: Gold | Revenue Score:  |
The program uses an array s[20] as stack with top as push / pop point. However, the push / pop operation should be implemented by declaring
struct stack
{
char s[20]; int top;
};
so that any direct manipulation of s[20] is avoided and the array as well as top element are accessed throuh struct stack variable
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