05 August 2008
完全二叉树结点个数
常规
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public int countNodes(TreeNode root) {
if (root == null){
return 0;
}
return countNodes(root.left) + countNodes(root.right) + 1;
}
高效
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/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public int countNodes(TreeNode root) {
if(root == null){
return 0;
}
int left = countLevel(root.left);
int right = countLevel(root.right);
if(left == right){
return countNodes(root.right) + (1<<left);
}else{
return countNodes(root.left) + (1<<right);
}
}
private int countLevel(TreeNode root){
int level = 0;
while(root != null){
level++;
root = root.left;
}
return level;
}
}