# include <stdio.h>
# include <string.h>
#
define MAX 20
void
infixtoprefix(char infix[20],char prefix[20]);
void
reverse(char array[30]);
char
pop();
void
push(char symbol);
int
isOperator(char symbol);
int
prcd(int symbol);
int
top=-1;
char
stack[MAX];
main()
{
char infix[20],prefix[20],temp;
printf("Enter infix operation:
");
gets(infix);
infixtoprefix(infix,prefix);
reverse(prefix);
puts((prefix));
}
void
infixtoprefix(char infix[20],char prefix[20]) {
int i,j=0;
char symbol;
stack[++top]='#';
reverse(infix);
for (i=0;i<strlen(infix);i++) {
symbol=infix[i];
if (isOperator(symbol)==0)
{
prefix[j]=symbol;
j++;
} else {
if
(symbol==')') {
push(symbol);
} else
if(symbol == '(') {
while
(stack[top]!=')') {
prefix[j]=pop();
j++;
}
pop();
} else {
if
(prcd(stack[top])<=prcd(symbol)) {
push(symbol);
}
else {
while(prcd(stack[top])>=prcd(symbol))
{
prefix[j]=pop();
j++;
}
push(symbol);
}
//end
for else
}
}
//end for else
}
//end for for
while (stack[top]!='#') {
prefix[j]=pop();
j++;
}
prefix[j]='\0';
}
void
reverse(char array[30])
{
int i,j;
char temp[100];
for
(i=strlen(array)-1,j=0;i+1!=0;--i,++j) {
temp[j]=array[i];
}
temp[j]='\0';
strcpy(array,temp);
}
char
pop() {
char a;
a=stack[top];
top--;
return a;
}
void
push(char symbol) {
top++;
stack[top]=symbol;
}
int
prcd(int symbol)
{
switch(symbol) {
case '+':
case '-':
return 2;
break;
case '*':
case '/':
return 4;
break;
case '$':
case '^':
return 6;
break;
case '#':
case '(':
case ')':
return 1;
break;
}
}
int
isOperator(char symbol) {
switch(symbol) {
case '+':
case '-':
case '*':
case '/':
case '^':
case '$':
case '&':
case '(':
case ')':
return 1;
break;
default:
return 0;
}
}
