0543-diameter-of-binary-tree.cpp

/*
 Given root of binary tree, return length of diameter of tree (longest path b/w any 2 nodes)

 Max path b/w 2 leaf nodes, "1 +" to add path

 Time: O(n)
 Space: O(n)
*/

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 * int val;
 * TreeNode *left;
 * TreeNode *right;
 * TreeNode() : val(0), left(nullptr), right(nullptr) {}
 * TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
*/
classSolution {
public:
intdiameterOfBinaryTree(TreeNode* root) {
int result = 0;
dfs(root, result);
return result;
 }
private:
intdfs(TreeNode* root, int& result) {
if (root == NULL) {
return0;
 }

int left = dfs(root->left, result);
int right = dfs(root->right, result);

 result = max(result, left + right);
return1 + max(left, right);
 }
};