标签：完全二叉树 which ast cep under can possible pre tween
Given a complete binary tree, count the number of nodes.
Definition of a complete binary tree from Wikipedia:
In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between 1 and 2h nodes inclusive at the last level h.
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解答
这道题目因为是完全二叉树，所以求节点数时可以做一下优化，当恰好全部充满时直接计算节点数，而不是继续用递归……否则有个点会过不去……
/** * Definition for a binary tree node. * struct TreeNode { * int val; * struct TreeNode *left; * struct TreeNode *right; * }; */ int countNodes(struct TreeNode* root) { int level = 0; struct TreeNode *node_1 = root, *node_2 = root; while(NULL != node_1&&NULL != node_2){ node_1 = node_1->left; node_2 = node_2->right; level++; } if(NULL != node_1){ return countNodes(root->left) + countNodes(root->right) + 1; } else{ return pow(2, level) - 1; } }
LeetCode OJ 222. Count Complete Tree Nodes
标签：完全二叉树 which ast cep under can possible pre tween
原文地址：http://www.cnblogs.com/YuNanlong/p/6033698.html
