Leetcode 104. Maximum Depth of Binary Tree

最新推荐文章于 2025-09-11 19:19:55 发布

ruihuank

最新推荐文章于 2025-09-11 19:19:55 发布

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本文介绍了一种求解二叉树最大深度的有效算法。通过递归深度优先搜索（DFS）及广度优先搜索（BFS）两种方法，实现对二叉树节点的遍历，以找出从根节点到最远叶子节点的最长路径。该算法适用于多种编程面试场景。

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.

Seen this question in a real interview before? YesNo

depth-first-search

/**
 * 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) {
        if (root == nullptr) return 0;
        return 1 + max(maxDepth(root->left), maxDepth(root->right));
    }
};

breadth-first-search

/**
 * 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) {
        if (root == nullptr) return 0;
        queue<TreeNode*> q;
        q.emplace(root);
        int ret = 0;

        while (!q.empty()) {
            ++ret;
            size_t n = q.size();
            for (size_t i = 0; i != n; ++i) {
                TreeNode* p = q.front();
                q.pop();
                if (p->left != nullptr) q.emplace(p->left);
                if (p->right != nullptr) q.emplace(p->right);
            }
        }

        return ret;

    }
};