54 lines
1.5 KiB
C++
54 lines
1.5 KiB
C++
// Source : https://leetcode.com/problems/count-complete-tree-nodes/
|
|
// Author : Hao Chen
|
|
// Date : 2015-06-12
|
|
|
|
/**********************************************************************************
|
|
*
|
|
* Given a complete binary tree, count the number of nodes.
|
|
*
|
|
* Definition of a complete binary tree from Wikipedia:
|
|
* http://en.wikipedia.org/wiki/Binary_tree#Types_of_binary_trees
|
|
*
|
|
* 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 2^h nodes inclusive at the last level h.
|
|
*
|
|
**********************************************************************************/
|
|
|
|
|
|
/**
|
|
* Definition for a binary tree node.
|
|
* struct TreeNode {
|
|
* int val;
|
|
* TreeNode *left;
|
|
* TreeNode *right;
|
|
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
|
|
* };
|
|
*/
|
|
class Solution {
|
|
public:
|
|
//return -1 if it is not.
|
|
int isCompleteTree(TreeNode* root) {
|
|
if (!root) return 0;
|
|
|
|
int cnt = 1;
|
|
TreeNode *left = root, *right = root;
|
|
for(; left && right; left=left->left, right=right->right) {
|
|
cnt *= 2;
|
|
}
|
|
|
|
if (left!=NULL || right!=NULL) {
|
|
return -1;
|
|
}
|
|
return cnt-1;
|
|
}
|
|
|
|
int countNodes(TreeNode* root) {
|
|
int cnt = isCompleteTree(root);
|
|
if (cnt != -1) return cnt;
|
|
int leftCnt = countNodes(root->left);
|
|
int rightCnt = countNodes(root->right);
|
|
return leftCnt + rightCnt + 1;
|
|
}
|
|
};
|