diff --git a/problems/0222.完全二叉树的节点个数.md b/problems/0222.完全二叉树的节点个数.md index 367fa717..64705ed6 100644 --- a/problems/0222.完全二叉树的节点个数.md +++ b/problems/0222.完全二叉树的节点个数.md @@ -194,7 +194,49 @@ public: Java: +```java +class Solution { + // 通用递归解法 + public int countNodes(TreeNode root) { + if(root == null) { + return 0; + } + return countNodes(root.left) + countNodes(root.right) + 1; + } +} +``` +```java +class Solution { + /** + * 针对完全二叉树的解法 + * + * 满二叉树的结点数为:2^depth - 1 + */ + public int countNodes(TreeNode root) { + if(root == null) { + return 0; + } + int leftDepth = getDepth(root.left); + int rightDepth = getDepth(root.right); + if (leftDepth == rightDepth) {// 左子树是满二叉树 + // 2^leftDepth其实是 (2^leftDepth - 1) + 1 ,左子树 + 根结点 + return (1 << leftDepth) + countNodes(root.right); + } else {// 右子树是满二叉树 + return (1 << rightDepth) + countNodes(root.left); + } + } + + private int getDepth(TreeNode root) { + int depth = 0; + while (root != null) { + root = root.left; + depth++; + } + return depth; + } +} +``` Python: