543. Diameter of Binary Tree

Posted 2020-10-11 andywu

Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longestpath between any two nodes in a tree. This path may or may not pass through the root.

Example:
Given a binary tree 

          1
         /         2   3
       / \     
      4   5    

Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].

题目含义：求二叉树的直径，并告诉了我们直径就是两点之间的最远距离。这条直径可以不包含根节点

 

 1     private int maxLength = 0;
 2     private int maxDepth(TreeNode root)
 3     {
 4         if (root == null)return 0;
 5         int leftMaxDepth = maxDepth(root.left);
 6         int rightMaxDepth = maxDepth(root.right);
 7         maxLength = Math.max(maxLength,leftMaxDepth+rightMaxDepth);
 8         return Math.max(leftMaxDepth,rightMaxDepth)+1;
 9     }    
10     public int diameterOfBinaryTree(TreeNode root) {
11         maxDepth(root);
12         return maxLength;
13     }