LeetCode104 - Maximum Depth of Binary Tree - 利用递归和非递归方法求二叉树的最大深度 - 输出二叉树每一层最右边的节点

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

递归：

/**
 * 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:
    int maxDepth(TreeNode* root) {
        if(root == NULL)
            return 0;
        int maxLeft=maxDepth(root->left);
        int maxRight=maxDepth(root->right);
        return maxLeft>maxRight?maxLeft+1:maxRight+1;
    
        }
        
};

非递归：利用树的层次遍历（使用队列），并记录每一层的节点个数。

 

/**
 * 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:
    int maxDepth(TreeNode* root) {
        if(root == NULL)
            return 0;
        queue<TreeNode *> q;
        q.push(root);
        int depth=0;// 记录深度
        while(!q.empty())
        {
            int len = q.size();//记录树当前层的结点个数
            ++depth;
            while(len)
            {
                TreeNode * p=q.front();
                if(p->left)
                    q.push(p->left);
                if(p->right)
                    q.push(p->right);
                q.pop();
                --len;
            }  
        }
        return depth;
    }
        
};

 输出二叉树每一层最右边的节点：len==1时对应的节点就是最右边的节点，输出即可。