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

Solution:

java

public class DiameterOfBinaryTree {
    // Approach 1
    public static int diameterOfBinaryTree(TreeNode root) {
        if (root == null)
            return 0;
        int dia1 = diameterOfBinaryTree(root.left);
        int dia2 = diameterOfBinaryTree(root.right);
        int dia3 = MaximumDepthOfBinaryTree.maxDepth(root.left) + MaximumDepthOfBinaryTree.maxDepth(root.right) + 1;
        return Math.max(Math.max(dia1, dia2), dia3);
    }

    // Approach 2
    int diameter = 0;

    public int diameterOfBinaryTree2(TreeNode root) {
        getDiameter(root);
        return diameter - 1;
    }

    private int getDiameter(TreeNode root) {
        if (root == null)
            return 0;
        int leftHeight = getDiameter(root.left);
        int rightHeight = getDiameter(root.right);
        diameter = Math.max(diameter, leftHeight + rightHeight + 1);
        return Math.max(leftHeight, rightHeight) + 1;
    }
}

class MaximumDepthOfBinaryTree {

    public static int maxDepth(TreeNode root) {
        if (root == null)
            return 0;
        int depth = Math.max(maxDepth(root.left), maxDepth(root.right)) + 1;
        return depth;
    }
}

543. Diameter of Binary Tree #

Problem Statement: #

Example 1: #

Example 2: #

Constraints: #

Solution: #

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