剑指offer——二叉树的深度

struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};

class Solution {
    public:
        int TreeDepth(TreeNode* pRoot){
            if(pRoot == NULL){
                return 0;
            }
            int left = this->TreeDepth(pRoot->left);
            int right = this->TreeDepth(pRoot->right);
            return (left>right)?left+1:right+1;
        }
};