LeetCode:Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

class Solution{
public:
    int maxDepth(TreeNode *root){
        if(root==NULL)
        {
            return 0;
        }
        int a=maxDepth(root->left);
        int b=maxDepth(root->right);
        return (a>b?a:b)+1;
    }
};