Leetcode 104. The maximum depth of a binary tree

subject

Ideas

• Determine the parameters and return values of recursive functions , The parameter is the root node of the binary tree , The return value is the depth of the tree
• Recursive export , Empty node , return 0
• Determine single level recursive logic ： First find the depth of the left subtree , Then find the depth of the right subtree , Then take the maximum depth plus one , Is the maximum depth of the current node

Code

/** * 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 {
    
public:
    int getDepth(TreeNode* root)
    {
    
        if(root == NULL)
        {
    
            return 0;//  Recursive export 
        }
        int leftDepth = getDepth(root->left);
        int rightDepth = getDepth(root->right);
        int depth = max(leftDepth,rightDepth) + 1;
        return depth;
    }

    int maxDepth(TreeNode* root) {
    
        return getDepth(root);
    }
};