543. Diameter of Binary Tree

Posted on Edited on In

543. Diameter of Binary Tree

Description

Difficulty: Easy

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

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:

1
2
3
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:

1
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

Hints/Notes

Solution

Language: C++

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
/**
 * 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) {}
 * };
 */
class Solution {
public:
    int res = 0;

    int diameterOfBinaryTree(TreeNode* root) {
        maxDepth(root);
        return res;
    }

    int maxDepth(TreeNode* root) {
        if (root == nullptr) {
            return 0;
        }
        int left = maxDepth(root->left);
        int right = maxDepth(root->right);
        res = max(left + right, res);
        return max(left, right) + 1;
    }
};