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437.swift
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437.swift
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// passed
/**
* Definition for a binary tree node.
* public class TreeNode {
* public var val: Int
* public var left: TreeNode?
* public var right: TreeNode?
* public init() { self.val = 0; self.left = nil; self.right = nil; }
* public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
* public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
* self.val = val
* self.left = left
* self.right = right
* }
* }
*/
// 速度比较慢
class Solution {
// 叶子的可能性 1种
// 子树的可能性:(左儿子的所有可能,右儿子的所有可能),自己,自己+左儿子(所有可能),自己+右儿子(所有可能),前两个已经被包含。
// 深度优先遍历,保存所有可能的值
func pathSum(_ root: TreeNode?, _ sum: Int) -> Int {
guard let root = root else { return 0 }
var allvals = [Int]()
func handle(_ node: TreeNode) -> ([Int]) {
var v = [node.val]
if let left = node.left {
v += (handle(left).map { $0 + node.val })
}
if let right = node.right {
v += (handle(right).map { $0 + node.val })
}
allvals += v
return v
}
handle(root)
let res = allvals.filter { $0 == sum }.count
return res
}
}