From 2069dddd3b1c8a5271d269f853c1e3f44e153962 Mon Sep 17 00:00:00 2001
From: nuomi1 <nuomi1@qq.com>
Date: Tue, 3 Jan 2023 22:24:50 +0800
Subject: [PATCH] feat: add Swift codes for space time tradeoff article

---
 codes/swift/Package.swift                     |  2 +
 .../leetcode_two_sum.swift                    | 46 +++++++++++++++++++
 .../space_time_tradeoff.md                    | 33 +++++++++++++
 3 files changed, 81 insertions(+)
 create mode 100644 codes/swift/chapter_computational_complexity/leetcode_two_sum.swift

diff --git a/codes/swift/Package.swift b/codes/swift/Package.swift
index 250c09af1..a292d9fd3 100644
--- a/codes/swift/Package.swift
+++ b/codes/swift/Package.swift
@@ -8,11 +8,13 @@ let package = Package(
         .executable(name: "time_complexity", targets: ["time_complexity"]),
         .executable(name: "worst_best_time_complexity", targets: ["worst_best_time_complexity"]),
         .executable(name: "space_complexity", targets: ["space_complexity"]),
+        .executable(name: "leetcode_two_sum", targets: ["leetcode_two_sum"]),
     ],
     targets: [
         .target(name: "utils", path: "utils"),
         .executableTarget(name: "time_complexity", path: "chapter_computational_complexity", sources: ["time_complexity.swift"]),
         .executableTarget(name: "worst_best_time_complexity", path: "chapter_computational_complexity", sources: ["worst_best_time_complexity.swift"]),
         .executableTarget(name: "space_complexity", dependencies: ["utils"], path: "chapter_computational_complexity", sources: ["space_complexity.swift"]),
+        .executableTarget(name: "leetcode_two_sum", path: "chapter_computational_complexity", sources: ["leetcode_two_sum.swift"]),
     ]
 )
diff --git a/codes/swift/chapter_computational_complexity/leetcode_two_sum.swift b/codes/swift/chapter_computational_complexity/leetcode_two_sum.swift
new file mode 100644
index 000000000..6ed0e580c
--- /dev/null
+++ b/codes/swift/chapter_computational_complexity/leetcode_two_sum.swift
@@ -0,0 +1,46 @@
+/*
+ * File: leetcode_two_sum.swift
+ * Created Time: 2023-01-03
+ * Author: nuomi1 (nuomi1@qq.com)
+ */
+
+func twoSumBruteForce(nums: [Int], target: Int) -> [Int] {
+    // 两层循环，时间复杂度 O(n^2)
+    for i in nums.indices.dropLast() {
+        for j in nums.indices.dropFirst(i + 1) {
+            if nums[i] + nums[j] == target {
+                return [i, j]
+            }
+        }
+    }
+    return [0]
+}
+
+func twoSumHashTable(nums: [Int], target: Int) -> [Int] {
+    // 辅助哈希表，空间复杂度 O(n)
+    var dic: [Int: Int] = [:]
+    // 单层循环，时间复杂度 O(n)
+    for i in nums.indices {
+        if let j = dic[target - nums[i]] {
+            return [j, i]
+        }
+        dic[nums[i]] = i
+    }
+    return [0]
+}
+
+@main
+enum LeetcodeTwoSum {
+    static func main() {
+        // ======= Test Case =======
+        let nums = [2, 7, 11, 15]
+        let target = 9
+        // ====== Driver Code ======
+        // 方法一
+        var res = twoSumBruteForce(nums: nums, target: target)
+        print("方法一 res = \(res)")
+        // 方法二
+        res = twoSumHashTable(nums: nums, target: target)
+        print("方法二 res = \(res)")
+    }
+}
diff --git a/docs/chapter_computational_complexity/space_time_tradeoff.md b/docs/chapter_computational_complexity/space_time_tradeoff.md
index 651aff148..0b86c11ca 100644
--- a/docs/chapter_computational_complexity/space_time_tradeoff.md
+++ b/docs/chapter_computational_complexity/space_time_tradeoff.md
@@ -149,6 +149,22 @@ comments: true
     }
     ```
 
+=== "Swift"
+
+    ```swift title="leetcode_two_sum.swift"
+    func twoSumBruteForce(nums: [Int], target: Int) -> [Int] {
+        // 两层循环，时间复杂度 O(n^2)
+        for i in nums.indices.dropLast() {
+            for j in nums.indices.dropFirst(i + 1) {
+                if nums[i] + nums[j] == target {
+                    return [i, j]
+                }
+            }
+        }
+        return [0]
+    }
+    ```
+
 ### 方法二：辅助哈希表
 
 时间复杂度 $O(N)$ ，空间复杂度 $O(N)$ ，属于「空间换时间」。
@@ -294,3 +310,20 @@ comments: true
         }
     }
     ```
+
+=== "Swift"
+
+    ```swift title="leetcode_two_sum.swift"
+    func twoSumHashTable(nums: [Int], target: Int) -> [Int] {
+        // 辅助哈希表，空间复杂度 O(n)
+        var dic: [Int: Int] = [:]
+        // 单层循环，时间复杂度 O(n)
+        for i in nums.indices {
+            if let j = dic[target - nums[i]] {
+                return [j, i]
+            }
+            dic[nums[i]] = i
+        }
+        return [0]
+    }
+    ```