LeetCodeSourceCode/104_maxDepth.cpp at main · AdamLin0108/LeetCodeSourceCode · GitHub

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#include <iostream>
#include <stack>
#include <algorithm> // for max
using namespace std;

// Definition for a binary tree node.
struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
};

class Solution {
public:
    int maxDepth(TreeNode* root) {
        if (!root) return 0;

        stack<pair<TreeNode*, int>> stk; // Pair of node and depth
        stk.push({root, 1});
        int maxDepth = 0;

        while (!stk.empty()) {
            auto [node, depth] = stk.top(); // Unpack pair
            stk.pop();

            if (node) {
                // Update the maximum depth
                maxDepth = max(maxDepth, depth);

                // Push children with incremented depth
                stk.push({node->left, depth + 1});
                stk.push({node->right, depth + 1});
            }
        }

        return maxDepth;
    }
};

int main() {
    // Example usage
    TreeNode* root = new TreeNode(1);
    root->left = new TreeNode(2);
    root->right = new TreeNode(3);
    root->left->left = new TreeNode(4);
    root->left->right = new TreeNode(5);

    Solution sol;
    cout << "Maximum Depth: " << sol.maxDepth(root) << endl;

    // Clean up memory
    delete root->left->left;
    delete root->left->right;
    delete root->left;
    delete root->right;
    delete root;

    return 0;
}


//=============================================
// Recursive Solution

#include <iostream>
using namespace std;

// Definition for a binary tree node.
struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
};

class Solution {
public:
    int maxDepth(TreeNode* root) {
        if (root == nullptr) return 0;
        int leftDepth = maxDepth(root->left);
        int rightDepth = maxDepth(root->right);
        return max(leftDepth, rightDepth) + 1;
    }
};

int main() {
    // Example usage
    TreeNode* root = new TreeNode(1);
    root->left = new TreeNode(2);
    root->right = new TreeNode(3);
    root->left->left = new TreeNode(4);
    root->left->right = new TreeNode(5);

    Solution sol;
    cout << "Maximum Depth (Recursive): " << sol.maxDepth(root) << endl;

    // Clean up memory
    delete root->left->left;
    delete root->left->right;
    delete root->left;
    delete root->right;
    delete root;

    return 0;
}