feat: Solution for August Challeng 28 - Implement Rand10() Using Rand7()

Author: milanpanchal

Swift/August Challenge/28_ImplementRand10()UsingRand7().playground/Contents.swift

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+/*:
+# Implement Rand10() Using Rand7()
+ https://leetcode.com/explore/challenge/card/august-leetcoding-challenge/552/week-4-august-22nd-august-28th/3439/
+
+ ---
+
+### Problem Statement:
+ 
+ Given the API `rand7` which generates a uniform random integer in the range 1 to 7, write a function `rand10` which generates a uniform random integer in the range 1 to 10. You can only call the API `rand7` and you shouldn't call any other API. Please don't use the system's `Math.random()`.
+
+ Notice that Each test case has one argument `n`, the number of times that your implemented function `rand10` will be called while testing.
+
+
+
+### Example:
+
+ ```
+ Input: n = 1
+ Output: [2]
+
+ Input: n = 2
+ Output: [2,8]
+
+ Input: n = 3
+ Output: [3,8,10]
+
+ ```
+ 
+ ### Constraints:
+ + 1 <= n <= 10^5
+
+ ### Follow up:
+ + What is the [expected](https://en.wikipedia.org/wiki/Expected_value) value for the number of calls to `rand7()` function?
+ + Could you minimize the number of calls to `rand7()`?
+ 
+ */
+
+
+import UIKit
+
+/**
+ * The rand7() API is already defined in the parent class SolBase.
+ * func rand7() -> Int = {}
+ * @return a random integer in the range 1 to 7
+ */
+
+class Solution: SolBase {
+    func rand10() -> Int {
+        let result = (rand7() - 1) * 7 + rand7()
+
+        if result <= 40 {
+            return result % 10 + 1
+        }
+
+        return rand10()
+    }
+}
+
+let sol = Solution()
+sol.rand10()

Swift/August Challenge/28_ImplementRand10()UsingRand7().playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' display-mode='raw'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>