How many distinct binary search trees can be created out of 4 distinct keys?

Postorder traversal of a given binary search tree T produces the following sequence of keys 10, 9, 23, 22, 27, 25, 15, 50, 95, 60, 40, 29 Which one of the following sequences of keys can be the result of an inorder traversal of the tree T?

The numbers 1, 2, ........, n are inserted in a binary search tree in some order. In the resulting tree, the right subtree of the root contains p nodes. The first number to be inserted in the tree must be

The following C function takes a single-linked list of integers as a parameter and rearranges the elements of the list. The function is called with the list containing the integers 1,2,3,4,5,6,7 in the given order. What will be the contents of the list after the function completes execution?

struct node { 
    int value; 
    struct node *next; 
}; 

Void rearrange (struct node *list ){ 
    struct node *p, * q; 
    int temp; 
    if( !list || !list-> next) return; 
    p = list; q = list->next; 
    while (q) { 
      temp = p->value; 
      p-> value = q ->value; 
      q-> value = temp; 
      p = q-> next; 
      q = p ? p->next : 0; 
    } 
}