二叉树的深度

二叉树的深度

题目描述

输入一棵二叉树，求该树的深度。从根结点到叶结点依次经过的结点（含根、叶结点）形成树的一条路径，最长路径的长度为树的深度。

利用队列的先进先出, 思想是弹出当前层, 插入下一层

class Solution {
public:
    int TreeDepth(TreeNode* pRoot)
    {
        if (nullptr == pRoot) 
            return 0;
        queue<TreeNode *> q;
        int depth = 0;
        q.push(pRoot);
        while (!q.empty()) {
            depth++;
            int size = q.size();
            // 由于for里面还有插入, 所以for循环结束不能直接用q.size()
            //for (int i = 0; i < q.size(); i++) {
            for (int i = 0; i < size; i++) {	// 弹出当前层, 插入下一层
                TreeNode *temp = q.front();
                q.pop();
                if (temp->left)    q.push(temp->left);
                if (temp->right)   q.push(temp->right);
            }
        }
        
        return depth;
    }
};

树的遍历, 插一句It doesn't work why, it works why?

class Solution {
public:
    
    int TreeDepth(TreeNode* pRoot)
    {
        int rightHigh = 1;
        int leftHigh = 1;
        
        if (nullptr == pRoot) {
            return 0;
        }
        
        if (nullptr != pRoot->left) {
            rightHigh += TreeDepth(pRoot->left);
        }
        
        if (nullptr != pRoot->right) {
            leftHigh += TreeDepth(pRoot->right);
        }
        
        return rightHigh > leftHigh ? rightHigh : leftHigh;
    }
};

/*
struct TreeNode {
	int val;
	struct TreeNode *left;
	struct TreeNode *right;
	TreeNode(int x) :
			val(x), left(NULL), right(NULL) {
	}
};*/