find preorder given postorder and inorder

it is the code of uva 536 http://ift.tt/19njc3i

But I want to ask,if the questions changes, that means asking preorder given postorder and inorder, how can i change my code???any one helps?it is urgent,thanks(NOT A HOMEWORK)

#include <stdio.h>
#include <string.h>
char inorder[100], preorder[100];
char line[200];
void trace(int ihead, int itail, int phead, int ptail)
{
char split = preorder[phead];
int i;
int len;
if (ihead > itail) return;
for (i=ihead; inorder[i] != split; ++i)   ;
       len = i - ihead;
     trace(ihead, i-1, phead+1, phead+len);
          len = itail - i - 1;
     trace(i+1, itail, ptail - len, ptail);
            printf("%c", split);
       }
    int main() {
         int n;
  for (;;) {
if (gets(line) == NULL) break;
  sscanf(line, "%s %s", preorder, inorder);
  n = strlen(inorder);
 trace(0, n-1, 0, n-1);
      printf("\n");}
   return 0;
            }