LeetCode 543---- Diameter of Binary Tree

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 longest path 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].

Note: The length of path between two nodes is represented by the number of edges between them.

对根节点递归计算左右子树的Diameter，通过和类内的变量 diameter 进行比较，保存较大值。在每一次递归结束后，返回这棵子树的深度，根节点获取了左右子树的深度后，将二者相加就是该根节点下的Diameter。

/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
int diameter=0;
public int diameterOfBinaryTree(TreeNode root) {
diameter=0;
getDepth(root);
return diameter;
}

public int getDepth(TreeNode root){
if(root==null){
return -1;
}
int leftDepth=getDepth(root.left);
int rightDepth=getDepth(root.right);
int temp=leftDepth+rightDepth+2;
if(temp>diameter){
diameter=temp;
}
return Math.max(leftDepth, rightDepth)+1;
}
}