LeetCode 104. Maximum Depth of Binary Tree

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.

这是个很简单的题目，只需对树进行深度遍历即可，如果某个节点的深度大于最大深度，则将最大深度的值改为这个深度

遍历结束后，这个最大深度即为所求值

/**
 * 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:
    void depthFirstSearch(TreeNode* root,int len)
    {
        if (!root)return;
        depthFirstSearch(root->left, len + 1);
        depthFirstSearch(root->right, len + 1);
        if (maxD < len+1)maxD = len+1;
    }
    int maxDepth(TreeNode* root) {
        depthFirstSearch(root, 0);
        return maxD;
    }
private:
    size_t maxD=0;
};