Consider the label sequences obtained by the following pairs of traversals on a labeled binary tree. Which of these pairs identify a tree uniquely?
i) preorder and postorder
ii) inorder and postorder
iii) preorder and inorder
iv) level order and postorder

Consider the following C program segment

struct CellNode{ 
    struct CellNode *leftChild; 
    int element; 
    struct CellNode *rightChild; 
  };
 
int Dosomething (struct CellNode *ptr) { 
      int value = 0; 
      if (ptr ! = NULL) 
          { if (ptr - > leftChild ! = NULL) 
            value = 1 + DoSomething (ptr - > leftChild); 
          if (ptr - > rightChild ! = NULL) 
            value = max(value,1 + DoSomething (ptr - > rightChild)); 
          } 
      return (value); 
} 

The value returned by the function DoSomething when a pointer to the root of a non-empty tree is passed as argument is

The number of leaf nodes in a rooted tree of n nodes, with each node having 0 or 3 children is:

Let LASTPOST, LASTIN and LASTPRE denote the last vertex visited in a postorder, inorder and preorder traversal. Respectively, of a complete binary tree. Which of the following is always tree?