687. Longest Univalue Path

Given the root of a binary tree, return 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.

The length of the path between two nodes is represented by the number of edges between them.

Example 1:

Input: root = [5,4,5,1,1,5]
Output: 2

Example 2:

Input: root = [1,4,5,4,4,5]
Output: 2

Constraints:

• The number of nodes in the tree is in the range [0, 104].
• -1000 <= Node.val <= 1000
• The depth of the tree will not exceed 1000.

# @lc code=start
using LeetCode

function longest_univalue_path(root::TreeNode{Int})
    res = 0
    function lup(root::TreeNode{Int})
        r2 = 1
        rl = lup(root.left)
        rr = lup(root.right)
        r = max(rl, rr) + 1
        if rl != 0 && root.val == root.left.val
            r2 += rl
        end
        if rr != 0 && root.val == root.right.val
            r2 += rr
        end
        res = max(r, res)
        return r
    end
    lup(::Nothing) = 0
    lup(root)
    return res - 1
end
# @lc code=end

longest_univalue_path (generic function with 1 method)

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