LeetCode题解之Diameter of Binary Tree

 1 int ans;
 2     int diameterOfBinaryTree(TreeNode* root) {
 3         ans = 1;
 4         depth(root);
 5         
 6         return ans - 1;
 7     }
 8     
 9     int depth(TreeNode *root){
10         if (root == NULL)
11             return 0;
12         int L = depth(root->left);
13         int R = depth(root->right);
14         ans = max(ans, L+R+1);
15         return max(L,R) + 1;
16     }