[leetcode #543] Diameter of Binary Tree
1609 ワード
Problem
Given the root of a binary tree, return 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.
The length of a path between two nodes is represented by the number of edges between them.
Example 1:
Input: root = [1,2,3,4,5]
Output: 3
Explanation: 3 is the length of the path [4,2,1,3] or [5,2,1,3].
Example 2:Input: root = [1,2]
Output: 1
Constraints:・ The number of nodes in the tree is in the range [1, 10⁴].
・ -100 <= Node.val <= 100
Idea
これは簡単な問題です.treeナビゲーション時に深さを測定し、遡及によって2つのサブノード間の長さを測定します.ノード全体をブラウズした後の最大長さは、ツリーの直径です.
Solution
class Solution {
int res;
public int diameterOfBinaryTree(TreeNode root) {
res = 0;
bfs(root);
return res;
}
private int bfs(TreeNode node) {
if (node == null)
return -1;
int left = 1 + bfs(node.left);
int right = 1 + bfs(node.right);
int depth = Math.max(left, right);
res = Math.max(res, left+right);
return depth;
}
}
Reference
https://leetcode.com/problems/diameter-of-binary-tree/
Reference
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