687. Longest Univalue Path 最长的唯一路径
Given a binary tree, find the length of the longest path where each node in the path has the same value. This path may or may not pass through the root.
Note: The length of path between two nodes is represented by the number of edges between them.
Example 1:
Input:
5 / \ 4 5 / \ \ 1 1 5
Output:
2
Example 2:
Input:
1 / \ 4 5 / \ \ 4 4 5
Output:
2
Note: The given binary tree has not more than 10000 nodes. The height of the tree is not more than 1000.
给定二叉树,找到路径中每个节点具有相同值的最长路径的长度。此路径可能通过或不能通过根。
let max = 0;
var longestUnivaluePath = function(root) {
max = 0;
helper(root, null);
return max;
};
var helper = (node,parentVal) => {
if (!node) return 0;
let left = helper(node.left, node.val);
let right = helper(node.right, node.val);
max = Math.max(left + right, max);
if (node.val == parentVal) {
return Math.max(left, right) + 1;
} else {
return 0;
}
}
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