A full binary tree, in which every node has either 0 or 2 children, has 10 internal nodes. How many leaves does it have?
Correct answer B. 11
Explanation
In a full binary tree the number of leaves is always one more than the number of internal nodes, L = I + 1. Each internal node contributes two child edges, so there are 2I edges, and since edges equal nodes minus one, 2I = I + L − 1, giving L = I + 1. With 10 internal nodes there are 11 leaves and 21 nodes in total.
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