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INFIX_TO_PREFIX.c
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INFIX_TO_PREFIX.c
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#include<stdio.h>
#define SIZE 50
#include<string.h>
char s[SIZE];
int top=-1;
push(char elem)
{
s[++top]=elem;
}
char pop()
{
return(s[top--]);
}
int pr(char elem)
{
switch(elem)
{
case ')': return 0;
case '+':
case '-': return 1;
case '*':
case '/': return 2;
}
}
main()
{
char infx[50],prfx[50],ch,elem;
int i=0,k=0;
printf("\n\nRead the Infix Expression ? ");
scanf("%s",infx);
strrev(infx);
while( (ch=infx[i++])!= '\0')
{
if( ch == ')') push(ch);
else
if(isalnum(ch)) prfx[k++]=ch;
else
if( ch == '(')
{
while( s[top]!= ')')
prfx[k++]=pop();
elem=pop();
}
else
{
while( pr(s[top]) > pr(ch) )
prfx[k++]=pop();
push(ch);
}
}
while( s[top] != '\0')
prfx[k++]=pop();
strrev(prfx);
strrev(infx);
printf("\n\nGiven Infix Expn: %s Prefix Expn: %s\n",infx,prfx);
}