031 作业提交

Week_01/id_31/LeetCode_21_031.swift

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+//
+//  LeetCode_21_031.swift
+//  TestCoding
+//
+//  Created by 龚欢 on 2019/4/15.
+//  Copyright © 2019 龚欢. All rights reserved.
+//
+
+import Foundation
+
+// 时间复杂度O(n) ; n为maxCount(l1.count, l2.count)
+class Solution {
+    func mergeTwoLists(_ l1: ListNode?, _ l2: ListNode?) -> ListNode? {
+        var result: [Int] = []
+
+        let a1 = converToArryFrom(l1)
+        let a2 = converToArryFrom(l2)
+
+        var i = 0
+        var j = 0
+
+        while true {
+            if (i >= a1.count || j >= a2.count) {
+                if (j <= a2.count - 1) { result = result + a2[j...a2.count - 1] }
+                if (i <= a1.count - 1) { result = result + a1[i...a1.count - 1] }
+                break;
+            }
+
+            if (a1[i] == a2[j]) {
+                result.append(a1[i])
+                result.append(a2[j])
+                i += 1
+                j += 1
+            } else if ((a1[i] < a2[j])) {
+                result.append(a1[i])
+                i += 1
+            } else {
+                result.append(a2[j])
+                j += 1
+            }
+        }
+        return convertToNodeFrom(result)
+    }
+
+    private func converToArryFrom(_ node: ListNode?) -> [Int] {
+        var resultArr: [Int] = []
+        guard let _ = node else { return resultArr }
+        var currentNode = node
+        while let current = currentNode {
+            resultArr.append(current.val)
+            currentNode = currentNode?.next
+        }
+        return resultArr
+    }
+
+    private func convertToNodeFrom(_ arr: [Int]) -> ListNode? {
+        guard arr.count > 0 else { return nil }
+        var result: ListNode?
+        var resultHeader: ListNode?
+        for v in arr {
+            if result == nil {
+                result = ListNode(v)
+                resultHeader = result
+            } else {
+                result?.next = ListNode(v)
+                result = result?.next
+            }
+        }
+        return resultHeader
+    }
+}

Week_01/id_31/LeetCode_24_031.swift

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+//
+//  LeetCode_24_031.swift
+//  TestCoding
+//
+//  Created by 龚欢 on 2019/4/15.
+//  Copyright © 2019 龚欢. All rights reserved.
+//
+
+import Foundation
+
+// 时间复杂度O(n) 
+class Solution {
+    var stack: [Int] = []
+    func swapPairs(_ head: ListNode?) -> ListNode? {
+        guard let h = head else { return nil }
+
+        var currentNode: ListNode? = head
+        var dump: ListNode? = ListNode(h.val)
+        let resultHeader: ListNode? = dump
+
+        while let current = currentNode {
+            if (stack.count == 0) {
+                stack.append(current.val)
+            } else {
+                let willPopNodeValue = stack.removeFirst()
+                dump?.next = ListNode(current.val)
+                dump = dump?.next
+                dump?.next = ListNode(willPopNodeValue)
+                dump = dump?.next
+            }
+            currentNode = currentNode?.next
+        }
+        if (stack.count > 0) { dump?.next = ListNode(stack[0])}
+
+        return resultHeader?.next
+    }
+}

Week_01/id_31/LeetCode_83_031.swift

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+//
+//  LeetCode_83_031.swift
+//  TestCoding
+//
+//  Created by 龚欢 on 2019/4/15.
+//  Copyright © 2019 龚欢. All rights reserved.
+//
+
+import Foundation
+
+// 解法1：时间复杂度O(n), 空间复杂度O(Node中不同的value的结点个数)
+class Solution {
+    var temp: [Int] = []
+    func deleteDuplicates(_ head: ListNode?) -> ListNode? {
+        guard let _ = head else { return nil }
+        var currentNode: ListNode? = head
+        var preNode: ListNode? = nil
+        var result: ListNode?
+        var resultHeader: ListNode?
+        while let current = currentNode {
+            if (temp.contains(current.val)) {
+                preNode?.next = currentNode?.next
+            } else {
+                if (result == nil) {
+                    result = ListNode(current.val)
+                    resultHeader = result
+                } else {
+                    result?.next = ListNode(current.val)
+                    result = result?.next
+                }
+                temp.append(current.val)
+            }
+            preNode = currentNode
+            currentNode = currentNode?.next
+        }
+        return resultHeader
+    }
+}
+
+// 解法2：时间复杂度O(2n), 空间复杂度O(Node中不同的value的结点个数)
+class Solution {
+    var temp: [Int] = []
+    func deleteDuplicates(_ head: ListNode?) -> ListNode? {
+        guard let _ = head else { return nil }
+        var currentNode: ListNode? = head
+        while let current = currentNode {
+            if (!temp.contains(current.val)) { temp.append(current.val) }
+            currentNode = currentNode?.next
+        }
+        return convertToNodeFrom(temp)
+    }
+
+    private func convertToNodeFrom(_ arr: [Int]) -> ListNode? {
+        guard arr.count > 0 else { return nil }
+        var result: ListNode?
+        var resultHeader: ListNode?
+        for v in temp {
+            if result == nil {
+                result = ListNode(v)
+                resultHeader = result
+            } else {
+                result?.next = ListNode(v)
+                result = result?.next
+            }
+        }
+        return resultHeader
+    }
+}

Week_01/id_31/LeetCode_905_031.swift

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+//
+//  LeetCode_905_031.swift
+//  TestCoding
+//
+//  Created by 龚欢 on 2019/4/15.
+//  Copyright © 2019 龚欢. All rights reserved.
+//
+
+import Foundation
+
+// 时间复杂度 O(n)
+// 方法 1
+class Solution {
+    func sortArrayByParity(_ A: [Int]) -> [Int] {
+        guard A.count > 0 else { return [] }
+        var tempA = A
+        var i = 0
+        var j = tempA.count - 1
+        while i <= j {
+            if (tempA[i] % 2 == 0) {
+                i += 1
+            } else {
+                if (tempA[j] % 2 == 0) {
+                    tempA.swapAt(i, j)
+                    j -= 1
+                    i += 1
+                } else {
+                    j -= 1
+                }
+            }
+        }
+        return tempA
+    }
+}
+
+// 方法 2
+class Solution {
+    func sortArrayByParity(_ A: [Int]) -> [Int] {
+        return A.filter { $0 % 2 == 0 } + A.filter { $0 % 2 != 0 }
+    }
+}

Week_01/id_31/LeetCode_922_031.swift

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+//
+//  LeetCode_922_031.swift
+//  TestCoding
+//
+//  Created by 龚欢 on 2019/4/15.
+//  Copyright © 2019 龚欢. All rights reserved.
+//
+
+import Foundation
+
+// 时间复杂度: O(n/2) 空间复杂度:O(n)
+class Solution {
+    func sortArrayByParityII(_ A: [Int]) -> [Int] {
+        guard A.count > 0 else { return [] }
+        var result: [Int] = []
+        let even = A.filter { $0 % 2 == 0 }
+        let odd  = A.filter { $0 % 2 != 0 }
+        for i in 0..<even.count {
+            result.append(even[i])
+            result.append(odd[i])
+        }
+        return result
+    }
+}