Add monte carlo pi calculation (#354)

Author: i-redbyte

math/pi/montecarlopi.go

@@ -0,0 +1,27 @@
+// montecarlopi.go
+// description: Calculating pi by the Monte Carlo method
+// details:
+// implementation of Monte Carlo Algorithm for the calculating of Pi - [Monte Carlo method](https://en.wikipedia.org/wiki/Monte_Carlo_method)
+// author(s) [red_byte](https://github.com/i-redbyte)
+// see montecarlopi_test.go
+
+package pi
+
+import (
+	"math/rand"
+	"time"
+)
+
+func MonteCarloPi(randomPoints int) float64 {
+	rnd := rand.New(rand.NewSource(time.Now().UnixNano()))
+	inside := 0
+	for i := 0; i < randomPoints; i++ {
+		x := rnd.Float64()
+		y := rnd.Float64()
+		if x*x+y*y <= 1 {
+			inside += 1
+		}
+	}
+	pi := float64(inside) / float64(randomPoints) * float64(4)
+	return pi
+}

math/pi/montecarlopi_test.go

@@ -0,0 +1,27 @@
+// montecarlopi_test.go
+// description: Test for calculating pi by the Monte Carlo method
+// author(s) [red_byte](https://github.com/i-redbyte)
+// see montecarlopi.go
+
+package pi
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestMonteCarloPi(t *testing.T) {
+	t.Run("Monte Carlo Pi", func(t *testing.T) {
+		result := fmt.Sprintf("%.2f", MonteCarloPi(100000000))
+		t.Log(result)
+		if result != "3.14" {
+			t.Errorf("Wrong result! Expected:%f, returned:%s ", 3.1415, result)
+		}
+	})
+}
+
+func BenchmarkMonteCarloPi(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		MonteCarloPi(100000000)
+	}
+}