[swift] LeetCode 543. Diameter of Binary Tree

Given a binary tree, you need to compute 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.

Example:
Given a binary tree
1
/ \
2 3
/ \
4 5
Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].

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

private var diameter = 0
private func diameterOfNode(_ root: TreeNode?) -> Int {
    var lv = 0, rv = 0

    if let l = root?.left {
        lv = 1 + diameterOfNode(l)
    }
    if let r = root?.right {
        rv = 1 + diameterOfNode(r)
    }
    diameter = max(diameter, lv + rv)
    return max(lv, rv)
}

func diameterOfBinaryTree(_ root: TreeNode?) -> Int {
    diameterOfNode(root)
    return diameter
}

private var diameter = 0

private func diameterOfNode(_ root: TreeNode?) -> Int {

var lv = 0, rv = 0

if let l = root?.left {

lv = 1 + diameterOfNode(l)

}

if let r = root?.right {

rv = 1 + diameterOfNode(r)

}

diameter = max(diameter, lv + rv)

return max(lv, rv)

}

func diameterOfBinaryTree(_ root: TreeNode?) -> Int {

diameterOfNode(root)

return diameter

}

❤ 点击这里 -> 订阅《PAT | 蓝桥 | LeetCode学习路径 & 刷题经验》by 柳婼

❤ 点击这里 -> 订阅《从放弃C语言到使用C++刷算法的简明教程》by 柳婼

❤ 点击这里 -> 订阅PAT甲级乙级、蓝桥杯、GPLT天梯赛、LeetCode题解离线版