A queue where elements are inserted or deleted from either end (front or rear) is called a:
A Deque allows insertion and deletion operations at both the front and rear ends. A deque supports insertFront, insertRear, deleteFront and deleteRear. Restricted deques may limit insertion or deletion to one end, but a general deque permits both ends.
In a Priority Queue implemented using a Max-Heap, which element is always dequeued first?
A Priority Queue serving highest-priority items first returns the max element at the root of a Max-Heap in O(log n) time. A max-heap places the maximum key at its root, so removal of the root returns the highest-priority item when larger values represent higher priority. The heap is then restored in O(log n).
What is the maximum number of nodes in a Binary Tree of height 'h' (where root is at height 0)?
For height h (0-indexed), the max nodes sum up a geometric series 1 + 2 + 4 + ... + 2^$h = 2^{h+1} - 1$. The number of nodes at level i is at most $2^i$. Summing levels 0 through h gives 1+2+...+2^$h = 2^{h+1}-1$; this is a maximum, not a requirement for every binary tree.
In a full binary tree with 'L' leaf nodes, how many nodes have exactly two children?
In a full binary tree, every internal node has exactly two children. If L is the number of leaves and I is the number of internal (degree-2) nodes, then $L = I + 1$, so $I = L - 1$. This identity is true only for a full (proper) binary tree, in which every internal node has exactly two children. For an arbitrary binary tree that may contain one-child nodes, the number of leaves alone does not determine the number of degree-2 nodes.
The in-order traversal of a Binary Search Tree (BST) always produces keys in:
In-order traversal visits left subtree, root, and right subtree. In a BST, this visits nodes in strictly increasing sorted order. In-order means Left, Root, Right. The BST ordering property places every key in the left subtree before the root and every key in the right subtree after it; duplicates require a consistent duplicate-key policy.