543. Diameter of Binary Tree

Problem Statement

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

Intuition

Find the max of l+r at each step
Basically longest node to longest

Links

https://leetcode.com/problems/diameter-of-binary-tree/description/

Video Links

Approach 1:

C++

class Solution {
public:
    int maxi=0;
    int find_ans(TreeNode* root){
        if(root==nullptr)
            return 0;

        int l = find_ans(root->left);
        int r = find_ans(root->right);

        maxi = max(maxi, l+r);

        return 1 + max(l,r);
    }

    int diameterOfBinaryTree(TreeNode* root) {
        find_ans(root);
        return maxi;
    }
};

Approach 2:

C++

Approach 3:

C++

Approach 4:

C++