求一棵树的最大深度

思路：广度优先搜索即可

1. class Solution {
2. public:
3. int maxDepth(TreeNode *root) {
4. int depth = 0;
5. if (!root)
6. return depth;
7. queue<TreeNode*> nodeQue;
8. nodeQue.push(root);
10. while (!nodeQue.empty())
11. {
12. depth++;
13. int qSize = nodeQue.size();
14. for (size_t i = 0; i < qSize; i++)
15. {
16. if (nodeQue.front()->left)
17. nodeQue.push(nodeQue.front()->left);
18. if (nodeQue.front()->right)
19. nodeQue.push(nodeQue.front()->right);
20. nodeQue.pop();
21. }
22. }
23. return depth;
26. }
27. };