Added rand5 problem

Author: Murillo2380

src/easy-two-sigma-rand5/README.md

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+# Description
+
+Good morning! Here's your coding interview problem for today.
+
+This problem was asked by Two Sigma.
+
+Using a function `rand7()` that returns an integer from `1` to `7` (inclusive) with uniform probability, implement a function `rand5()` that returns an integer from `1` to `5` (inclusive).
+
+# Source
+
+Received by email from the [Daily Coding Problem](https://www.dailycodingproblem.com)

src/easy-two-sigma-rand5/java/Idea.md

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+# Idea behind the solution
+
+Similar to the fair coin problem, we just need to use the function `rand7()` until we get something between `1` and `5` since we were told in advance that `rand7()` is already supposed to be unbiased.

src/easy-two-sigma-rand5/java/Solution.java

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+import java.util.HashMap;
+import java.util.Map;
+
+public class Solution {
+
+    static int rand7() {
+        return (int) (Math.random() * 6d + 1d);
+    }
+
+    static int rand5() {
+
+        int number;
+        do {
+            number = rand7();
+        } while (number > 5);
+
+        return number;
+    }
+
+    static void printKeyMap(int key, int value) {
+        System.out.println(key + ":" + value);
+    }
+
+    public static void main(String[] args) {
+
+        Map<Integer, Integer> count = new HashMap<>();
+        for (int i = 0; i < 500; i++) {
+            final int num = rand5();
+            final int current = count.getOrDefault(num, 0);
+            count.put(num, current + 1);
+        }
+
+        count.forEach(Solution::printKeyMap); // On average each will have a count of more or less 100
+    }
+
+}