题解 | #二叉树的最大深度#

/**
 * struct TreeNode {
 *  int val;
 *  struct TreeNode *left;
 *  struct TreeNode *right;
 *  TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
#include <queue>
class Solution {
  public:
    // 层序遍历
    void treeTrave(int& depth, TreeNode* root) {
        queue<TreeNode*> fatherNodes, childNodes;
        fatherNodes.push(root);
        depth = 1;

        while (!fatherNodes.empty()) {
            auto node = fatherNodes.front();
            if (node->left != nullptr) {
                childNodes.push(node->left);
            }
            if (node->right != nullptr) {
                childNodes.push(node->right);
            }
            fatherNodes.pop();
            if (fatherNodes.empty() && !childNodes.empty()) {
                while (!childNodes.empty()) {
                    fatherNodes.push(childNodes.front());
                    childNodes.pop();
                }
                depth++;
            }
            else if (fatherNodes.empty() && childNodes.empty()) {
                break;
            }
        }
    }
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param root TreeNode类
     * @return int整型
     */
    int maxDepth(TreeNode* root) {
        // write code here
        if (root == nullptr) {
            return 0;
        }
        int depth = 0;
        treeTrave(depth, root);
        return depth;
    }
};