Lowest Common Ancestor of Deepest Leaves（C++最深葉節點的最近公共祖先）

解題思路：

（1）标記每個節點是否包含最深葉子結點

參考網址：https://leetcode.com/problems/lowest-common-ancestor-of-deepest-leaves/discuss/334577/JavaC%2B%2BPython-Two-Recursive-Solution

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
private:
    TreeNode *temp=NULL;
    int deepest = 0;
public:
    int postorder(TreeNode *root,int depth) {
        deepest = max(deepest,depth);
        if(!root) return depth;
        auto left=postorder(root->left,depth+1);
        auto right=postorder(root->right,depth+1);
        
        if(left==deepest && right==deepest) {
            temp=root;
        }
        return max(left,right);
    }
    
    TreeNode* lcaDeepestLeaves(TreeNode* root) {
        postorder(root,0);
        return temp;
    }
};