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) {}
 * };
 */
class Solution {
public:
    /**
     * 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
        //DFS
        /*
        if(root == nullptr)
        {
            return 0;
        }
        int leftHeight = maxDepth(root->left) + 1;
        int rightHeight = maxDepth(root->right) + 1;
        return std::max(leftHeight,rightHeight);
        */

        //BFS 
        if(root == nullptr)
        {
            return 0;
        }
        queue<TreeNode*>queue;
        queue.push(root);
        int step = 0;
        while(!queue.empty())
        {
            int levelSize = queue.size();
            for(int i = 0;i<levelSize;++i)
            {
                TreeNode*cur = queue.front();
                queue.pop();
                if(cur->left)
                {
                    queue.push(cur->left);
                }
                if(cur->right)
                {
                    queue.push(cur->right);
                }
            }
            step++;
        }
        return step;
      

    }
};