Given a binary tree, count the number of uni-value subtrees.
A Uni-value subtree means all nodes of the subtree have the same value.
Example :
Input: root = [5,1,5,5,5,null,5] 5 / 1 5 / \ 5 5 5 Output: 4
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class Solution { int res = 0; public int countUnivalSubtrees(TreeNode root) { helper(root); return res; } private boolean helper(TreeNode root) { if (root == null) { return true; } boolean left = helper(root.left); boolean right = helper(root.right); if (left && right) { if (root.left != null && root.left.val != root.val) { return false; } if (root.right != null && root.right.val != root.val) { return false; } res += 1; return true; } /** another way if (left && right && (root.left == null || root.val == root.left.val) && (root.right == null || root.val == root.right.val)) { res++; return true; } */ return false; } }
原文地址:https://www.cnblogs.com/xuanlu/p/12191184.html
时间: 2024-10-29 03:39:05