104. Maximum Depth of Binary Tree (Tree; DFS)

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.

class Solution {
public:
    int maxDepth(TreeNode *root) {
        if(!root) return 0;
        max_depth = 0;
        dfs(root,1);
        return max_depth;    
    }
    void dfs(TreeNode * current, int depth)
    {
        if(current->left) 
        {
            dfs(current->left, depth+1);
        }
        if (current->right)
        {
            dfs(current->right,depth+1);
        }
        if(!current->left && !current->right)
        {
            if(depth > max_depth){
                max_depth = depth;
            }
        }  
    }
private:
    int max_depth;
};