[swift] LeetCode 437. Path Sum III

You are given a binary tree in which each node contains an integer value.

Find the number of paths that sum to a given value.

The path does not need to start or end at the root or a leaf, but it must go downwards (traveling only from parent nodes to child nodes).

The tree has no more than 1,000 nodes and the values are in the range -1,000,000 to 1,000,000.

Example:

root = [10,5,-3,3,2,null,11,3,-2,null,1], sum = 8

10
/ \
5 -3
/ \ \
3 2 11
/ \ \
3 -2 1

Return 3. The paths that sum to 8 are:

1. 5 -> 3
2. 5 -> 2 -> 1
3. -3 -> 11

func pathSum(_ root: TreeNode?, _ sum: Int) -> Int {
    return pathSumNote(root, sum).0
}

private func pathSumNote(_ root: TreeNode?, _ sum: Int) -> (Int, [Int]) {
    guard let p = root else { return (0, []) }

    let ls = pathSumNote(p.left, sum)
    let rs = pathSumNote(p.right, sum)
    let arr = (ls.1 + rs.1).map({$0 + p.val}) + [p.val]

    let sum = ls.0 + rs.0 + arr.filter({$0 == sum}).count
    return (sum, arr)
}

func pathSum(_ root: TreeNode?, _ sum: Int) -> Int {

return pathSumNote(root, sum).0

}

private func pathSumNote(_ root: TreeNode?, _ sum: Int) -> (Int, [Int]) {

guard let p = root else { return (0, []) }

let ls = pathSumNote(p.left, sum)

let rs = pathSumNote(p.right, sum)

let arr = (ls.1 + rs.1).map({$0 + p.val}) + [p.val]

let sum = ls.0 + rs.0 + arr.filter({$0 == sum}).count

return (sum, arr)

}

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