diameter_binarytree.cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 * int val;
 * TreeNode *left;
 * TreeNode *right;
 * TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
 int diameterOfBinaryTree(TreeNode* root) {
 if(root==NULL)
 {
 return 0;
 }
 int option1 = height(root->left) + height(root->right);
 int option2 = diameterOfBinaryTree(root->right);
 int option3 = diameterOfBinaryTree(root->left);
 return max(option1,max(option2,option3));

 }
 int height(TreeNode* root){
 if(root==NULL)
 {
 return 0;
 }
 int lef = height(root->left);
 int righ = height(root->right);
 return 1 + max(lef,righ);
 }
};