0543. Diameter of Binary Tree.md

Tree

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
// The main function that computes the diameter of a binary tree
var diameterOfBinaryTree = function(root) {
    // Initialize the diameter variable to 0
    let diameter = 0;
    // Call the DFS function to compute the height of each node
    dfs(root);
    // Return the maximum path length (diameter) found
    return diameter;

    // The DFS function that computes the height of each node
    function dfs(root) {
        // Base case: the height of a null node is 0
        if(!root) return 0;
        // Recursively compute the height of the left and right subtrees
        let left = dfs(root.left);
        let right = dfs(root.right);
        // Update the diameter if the current node's diameter is greater than the previous maximum
        diameter = Math.max(diameter, left + right);
        // Return the height of the current node (maximum of the heights of the left and right subtrees plus one)
        return Math.max(left, right) + 1;
    }
};