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Commit ca67b79

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feat: add swift implementation to lcci problem: No.04.09 (doocs#2660)
1 parent 1e45282 commit ca67b79

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‎lcci/04.09.BST Sequences/README.md‎

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## 解法
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<!-- tabs:start -->
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```swift
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/* class TreeNode {
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* var val: Int
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* var left: TreeNode?
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* var right: TreeNode?
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*
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* init(_ val: Int, _ left: TreeNode? = nil, _ right: TreeNode? = nil) {
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* self.val = val
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* self.left = left
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* self.right = right
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* }
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* }
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*/
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class Solution {
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func BSTSequences(_ root: TreeNode?) -> [[Int]] {
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guard let root = root else { return [[]] }
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var result = [[Int]]()
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let prefix = [root.val]
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let leftSeq = BSTSequences(root.left)
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let rightSeq = BSTSequences(root.right)
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for left in leftSeq {
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for right in rightSeq {
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var weaved = [[Int]]()
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weaveLists(left, right, &weaved, prefix)
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result.append(contentsOf: weaved)
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}
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}
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return result
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}
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private func weaveLists(_ first: [Int], _ second: [Int], _ results: inout [[Int]], _ prefix: [Int]) {
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if first.isEmpty || second.isEmpty {
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var result = prefix
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result.append(contentsOf: first)
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result.append(contentsOf: second)
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results.append(result)
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return
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}
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var prefixWithFirst = prefix
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prefixWithFirst.append(first.first!)
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weaveLists(Array(first.dropFirst()), second, &results, prefixWithFirst)
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var prefixWithSecond = prefix
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prefixWithSecond.append(second.first!)
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weaveLists(first, Array(second.dropFirst()), &results, prefixWithSecond)
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}
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}
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```
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<!-- tabs:end -->
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<!-- end -->

‎lcci/04.09.BST Sequences/README_EN.md‎

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## Solutions
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<!-- tabs:start -->
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```swift
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/* class TreeNode {
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* var val: Int
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* var left: TreeNode?
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* var right: TreeNode?
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*
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* init(_ val: Int, _ left: TreeNode? = nil, _ right: TreeNode? = nil) {
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* self.val = val
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* self.left = left
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* self.right = right
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* }
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* }
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*/
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class Solution {
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func BSTSequences(_ root: TreeNode?) -> [[Int]] {
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guard let root = root else { return [[]] }
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var result = [[Int]]()
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let prefix = [root.val]
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let leftSeq = BSTSequences(root.left)
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let rightSeq = BSTSequences(root.right)
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for left in leftSeq {
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for right in rightSeq {
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var weaved = [[Int]]()
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weaveLists(left, right, &weaved, prefix)
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result.append(contentsOf: weaved)
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}
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}
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return result
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}
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private func weaveLists(_ first: [Int], _ second: [Int], _ results: inout [[Int]], _ prefix: [Int]) {
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if first.isEmpty || second.isEmpty {
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var result = prefix
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result.append(contentsOf: first)
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result.append(contentsOf: second)
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results.append(result)
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return
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}
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var prefixWithFirst = prefix
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prefixWithFirst.append(first.first!)
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weaveLists(Array(first.dropFirst()), second, &results, prefixWithFirst)
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var prefixWithSecond = prefix
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prefixWithSecond.append(second.first!)
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weaveLists(first, Array(second.dropFirst()), &results, prefixWithSecond)
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}
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}
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```
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<!-- tabs:end -->
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<!-- end -->
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/* class TreeNode {
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* var val: Int
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* var left: TreeNode?
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* var right: TreeNode?
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*
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* init(_ val: Int, _ left: TreeNode? = nil, _ right: TreeNode? = nil) {
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* self.val = val
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* self.left = left
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* self.right = right
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* }
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* }
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*/
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class Solution {
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func BSTSequences(_ root: TreeNode?) -> [[Int]] {
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guard let root = root else { return [[]] }
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var result = [[Int]]()
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let prefix = [root.val]
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let leftSeq = BSTSequences(root.left)
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let rightSeq = BSTSequences(root.right)
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for left in leftSeq {
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for right in rightSeq {
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var weaved = [[Int]]()
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weaveLists(left, right, &weaved, prefix)
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result.append(contentsOf: weaved)
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}
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}
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return result
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}
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private func weaveLists(_ first: [Int], _ second: [Int], _ results: inout [[Int]], _ prefix: [Int]) {
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if first.isEmpty || second.isEmpty {
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var result = prefix
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result.append(contentsOf: first)
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result.append(contentsOf: second)
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results.append(result)
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return
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}
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var prefixWithFirst = prefix
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prefixWithFirst.append(first.first!)
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weaveLists(Array(first.dropFirst()), second, &results, prefixWithFirst)
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var prefixWithSecond = prefix
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prefixWithSecond.append(second.first!)
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weaveLists(first, Array(second.dropFirst()), &results, prefixWithSecond)
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}
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}

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