maxDepth.cpp

#include <vector>
#include <iostream>
#include <unordered_map>

using namespace std;

// 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) {
        int max = 1;
        if (root == NULL)
            return 1;
        search(root, 1, &max);
        return max;
    }
    
    int search(TreeNode* root, int depth, int* max) {
        if (root->left == NULL && root->right == NULL) {
            if (depth > *max)
                *max = depth;
            return depth;
        } else {
            if (root->left != NULL) {
                search(root->left, depth+1, max);
            }
            if (root->right != NULL) {
                search(root->right, depth+1, max);
            }
            return depth;
        }
    }
};

int main(int argc, char**argv) {
    
    // [3,9,20,null,null,15,7],

    auto node1 = TreeNode(3);
    auto node2 = TreeNode(9);
    auto node3 = TreeNode(20);
    auto node4 = TreeNode(15);
    auto node5 = TreeNode(7);

    node1.left = &node2;
    node1.right = &node3;

    node3.left = &node4;
    node3.right = &node5;

    auto obj = Solution();

    int a = obj.maxDepth(&node1);

    return 0;
}