From 6a2d65b07bc5127bebefd53bb0f257f218e0c859 Mon Sep 17 00:00:00 2001
From: Lanre Adedara <lanre.adedara@shara.co>
Date: Mon, 8 Jul 2024 09:11:09 +0100
Subject: [PATCH] feat: add swift implementation to lcof2 problem: No.071

---
 .../README.md"                                | 38 +++++++++++++++++++
 .../Solution.swift"                           | 33 ++++++++++++++++
 2 files changed, 71 insertions(+)
 create mode 100644 "lcof2/\345\211\221\346\214\207 Offer II 071. \346\214\211\346\235\203\351\207\215\347\224\237\346\210\220\351\232\217\346\234\272\346\225\260/Solution.swift"

diff --git "a/lcof2/\345\211\221\346\214\207 Offer II 071. \346\214\211\346\235\203\351\207\215\347\224\237\346\210\220\351\232\217\346\234\272\346\225\260/README.md" "b/lcof2/\345\211\221\346\214\207 Offer II 071. \346\214\211\346\235\203\351\207\215\347\224\237\346\210\220\351\232\217\346\234\272\346\225\260/README.md"
index fc2a5d09cc0be..594fa816f1d18 100644
--- "a/lcof2/\345\211\221\346\214\207 Offer II 071. \346\214\211\346\235\203\351\207\215\347\224\237\346\210\220\351\232\217\346\234\272\346\225\260/README.md"	
+++ "b/lcof2/\345\211\221\346\214\207 Offer II 071. \346\214\211\346\235\203\351\207\215\347\224\237\346\210\220\351\232\217\346\234\272\346\225\260/README.md"	
@@ -222,6 +222,44 @@ func (this *Solution) PickIndex() int {
  */
 ```
 
+#### Swift
+
+```swift
+class Solution {
+    private var presum: [Int]
+
+    init(_ w: [Int]) {
+        let n = w.count
+        presum = [Int](repeating: 0, count: n + 1)
+        for i in 0..<n {
+            presum[i + 1] = presum[i] + w[i]
+        }
+    }
+
+    func pickIndex() -> Int {
+        let n = presum.count
+        let x = Int.random(in: 1...presum[n - 1])
+        var left = 0
+        var right = n - 2
+        while left < right {
+            let mid = (left + right) >> 1
+            if presum[mid + 1] >= x {
+                right = mid
+            } else {
+                left = mid + 1
+            }
+        }
+        return left
+    }
+}
+/**
+ * Your Solution object will be instantiated and called as such:
+ * let w = [1]
+ * let solution = Solution(w)
+ * solution.pickIndex()
+ */
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->
diff --git "a/lcof2/\345\211\221\346\214\207 Offer II 071. \346\214\211\346\235\203\351\207\215\347\224\237\346\210\220\351\232\217\346\234\272\346\225\260/Solution.swift" "b/lcof2/\345\211\221\346\214\207 Offer II 071. \346\214\211\346\235\203\351\207\215\347\224\237\346\210\220\351\232\217\346\234\272\346\225\260/Solution.swift"
new file mode 100644
index 0000000000000..3ae91801c5284
--- /dev/null
+++ "b/lcof2/\345\211\221\346\214\207 Offer II 071. \346\214\211\346\235\203\351\207\215\347\224\237\346\210\220\351\232\217\346\234\272\346\225\260/Solution.swift"	
@@ -0,0 +1,33 @@
+class Solution {
+    private var presum: [Int]
+
+    init(_ w: [Int]) {
+        let n = w.count
+        presum = [Int](repeating: 0, count: n + 1)
+        for i in 0..<n {
+            presum[i + 1] = presum[i] + w[i]
+        }
+    }
+
+    func pickIndex() -> Int {
+        let n = presum.count
+        let x = Int.random(in: 1...presum[n - 1])
+        var left = 0
+        var right = n - 2
+        while left < right {
+            let mid = (left + right) >> 1
+            if presum[mid + 1] >= x {
+                right = mid
+            } else {
+                left = mid + 1
+            }
+        }
+        return left
+    }
+}
+/**
+ * Your Solution object will be instantiated and called as such:
+ * let w = [1]
+ * let solution = Solution(w)
+ * solution.pickIndex()
+ */
\ No newline at end of file