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：
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.
解释下题目：
找到一棵树里的最长路径，该路径可能不经过根节点
1. 递归
实际耗时：0ms
int globalMax = 0;
public int diameterOfBinaryTree(TreeNode root) {
helper(root);
return globalMax;
}
private int helper(TreeNode root) {
if (root == null) {
return 0;
} else {
int left = helper(root.left);
int right = helper(root.right);
globalMax = Math.max(globalMax, left + right);
return Math.max(left, right) + 1;
}
}
思路其实跟寻找最深子树是一样的，只不过多了一个全局变量用来记录一下最长的距离而已。
