[LeetCode] 687. Longest Univalue Path

轉自LeetCode

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.

<Solution>

想法如下

• 利用 recursive 去計算每個 node 的最大 path 數，過程中並紀錄 global max 是多少

• 先用 recursive 去計算左右子樹的path各是多少，然後檢查當前的 node 和它的子節點的數值是不是一樣，是的話其 path 再加 1，也就是當前的 node 和它的子節點的這個 path

• 每個 recursive 回傳的是當前節點的最大 path 值

code 如下

Java

kotlin