二叉树的深度

非递归解法，利用队列

class Solution {
public:
    int TreeDepth(TreeNode* pRoot)
    {
        if(!pRoot){
            return 0;
        }
        queue<TreeNode*> q;
        int depth = 0;
        q.push(pRoot);
        while(!q.empty()){
            int len = q.size();
            while(len--){
                TreeNode* tmp = q.front();
                q.pop();
                if(len == 0){
                    depth++;
                }
                if(tmp->left){
                    q.push(tmp->left);
                }
                if(tmp->right){
                    q.push(tmp->right);
                }
            }

        }
        return depth;
    }
};