543

543. Diameter of Binary Tree (Easy)

Given the root of a binary tree, return the length of the diameter of the tree.

The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.

The length of a path between two nodes is represented by the number of edges between them.

 

Example 1:

Input: root = [1,2,3,4,5]
Output: 3
Explanation: 3 is the length of the path [4,2,1,3] or [5,2,1,3].

Example 2:

Input: root = [1,2]
Output: 1

 

Constraints:

• The number of nodes in the tree is in the range [1, 104].
• -100 <= Node.val <= 100

Companies:
Facebook, Amazon, Google, Microsoft, Bloomberg, Apple, Adobe, Tesla, Intuit

Related Topics:
Tree, Depth-First Search, Binary Tree

Similar Questions:

• Diameter of N-Ary Tree (Medium)

Solution 1. Post-order traversal

// OJ: https://leetcode.com/problems/diameter-of-binary-tree/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(H)
class Solution {
    int ans = 0;
    int postorder(TreeNode *root) {
        if (!root) return 0;
        int left = postorder(root->left), right = postorder(root->right);
        ans = max(ans, left + right);
        return 1 + max(left, right);
    }
public:
    int diameterOfBinaryTree(TreeNode* root) {
        postorder(root);
        return ans;
    }
};