Leetcode-Problems/Diameter-BinaryTree.java at main · kinshuk-code-1729/Leetcode-Problems · GitHub

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/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public int diameterOfBinaryTree(TreeNode root) {
        int[] dia = new int[1];
        height(root, dia);
        return dia[0];
    }

    private int height(TreeNode root, int[] dia){
        if(root == null){
            return 0;
        }

        int leftHeight = height(root.left, dia);
        int rightHeight = height(root.right, dia);
        dia[0] = Math.max(dia[0], leftHeight + rightHeight);
        return 1 + Math.max(leftHeight, rightHeight);
    }
}