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82 lines
1.4 KiB
Markdown
82 lines
1.4 KiB
Markdown
# [222. Count Complete Tree Nodes](https://leetcode.com/problems/count-complete-tree-nodes/)
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## 题目
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Given a complete binary tree, count the number of nodes.
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**Note**:
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Definition of a complete binary tree from Wikipedia:
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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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**Example**:
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```
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Input:
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1
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/ \
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2 3
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/ \ /
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4 5 6
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Output: 6
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```
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## 题目大意
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输出一颗完全二叉树的结点个数。
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## 解题思路
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这道题其实按照层序遍历一次树，然后把每一层的结点个数相加即可。
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## 代码
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```go
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package leetcode
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/**
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* Definition for a binary tree node.
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* type TreeNode struct {
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* Val int
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* Left *TreeNode
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* Right *TreeNode
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* }
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*/
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func countNodes(root *TreeNode) int {
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if root == nil {
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return 0
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}
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queue := []*TreeNode{}
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queue = append(queue, root)
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curNum, nextLevelNum, res := 1, 0, 1
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for len(queue) != 0 {
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if curNum > 0 {
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node := queue[0]
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if node.Left != nil {
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queue = append(queue, node.Left)
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nextLevelNum++
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}
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if node.Right != nil {
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queue = append(queue, node.Right)
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nextLevelNum++
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}
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curNum--
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queue = queue[1:]
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}
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if curNum == 0 {
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res += nextLevelNum
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curNum = nextLevelNum
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nextLevelNum = 0
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}
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}
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return res
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}
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``` |