已知 前序和中序遍歷 求後序遍歷序列

struct node *creat(char *a, char *b, int n)
  {
   struct node *ptr;
   char *p;
   int count = 0;
   if (n <= 0)
     return NULL;
    ptr = (struct node *)malloc(sizeof(struct node));
    ptr -> data = *a;
    for (p = &b[0]; p <= b + n - 1;p ++)
    {
     if (*p == *a)
       break
 
;
    }
    count = p - b;
    ptr -> l = creat(a + 1, b, count);
    ptr -> r = creat(a + 1 + count, p + 1, n - 1 - count);
   return ptr;
  }

已知中序和後序遍歷 求前序遍歷序列

struct node *creat(char *a, char *b, int n)
  {
   struct node *ptr;
   if (n <= 0)
     return NULL;
    ptr = (struct node *)malloc
 
(sizeof(struct node));
    ptr -> data = b[n - 1];
   int q = strchr(a, b[n - 1]) - a;
   ptr -> l = creat(a, b, q);
   ptr -> r = creat(a + q + 1, b + q, n - q - 1);
   return ptr;
  }