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

A program attempts to generate as many permutation as possible of the string “abcd” by pushing the character a,b,c,d in the same order onto a stack, but it may pop off the top character at any time. Which one of the following a strings CANNOT be generated using this program?

The best data structure to check whether an arithmetic expression has balanced parentheses is a

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