From a19f381ea79fdd744aeda156c1c13ab03169c656 Mon Sep 17 00:00:00 2001
From: VicRen <vic.ren@me.com>
Date: Sun, 11 Oct 2020 17:56:20 +0800
Subject: [PATCH] highly divisible triangular number

---
 highly_divisible_triangular_number/main.go    |  54 ++++++++
 .../triangular_number_test.go                 | 125 ++++++++++++++++++
 2 files changed, 179 insertions(+)
 create mode 100644 highly_divisible_triangular_number/main.go
 create mode 100644 highly_divisible_triangular_number/triangular_number_test.go

diff --git a/highly_divisible_triangular_number/main.go b/highly_divisible_triangular_number/main.go
new file mode 100644
index 0000000..f3e9201
--- /dev/null
+++ b/highly_divisible_triangular_number/main.go
@@ -0,0 +1,54 @@
+package main
+
+import "fmt"
+
+func main() {
+	n := 1
+	d := 1
+	for Tau(d) <= 500 {
+		n++
+		d += n
+	}
+
+	fmt.Println("num is", d, n)
+}
+
+func Tau(num int) int {
+	if num == 1 {
+		return 1
+	}
+	n := num
+	i := 2
+	p := 1
+
+	for i*i < n {
+		c := 1
+		for n%i == 0 {
+			n /= i
+			c++
+		}
+		i++
+		p *= c
+	}
+
+	if n == num || n > 1 {
+		p *= 1 + 1
+	}
+
+	return p
+}
+
+func GetTriangularNumber(count int) int {
+	ret := count * (count + 1) / 2
+	return ret
+}
+
+func ListDivisors(input int) []int {
+	var ret []int
+	for i := 1; i <= input; i++ {
+		if input%i == 0 {
+			ret = append(ret, i)
+		}
+	}
+	return ret
+}
diff --git a/highly_divisible_triangular_number/triangular_number_test.go b/highly_divisible_triangular_number/triangular_number_test.go
new file mode 100644
index 0000000..0a45bcf
--- /dev/null
+++ b/highly_divisible_triangular_number/triangular_number_test.go
@@ -0,0 +1,125 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestTau(t *testing.T) {
+	tt := []struct {
+		name  string
+		input int
+		want  int
+	}{
+		{
+			"1",
+			1,
+			1,
+		},
+		{
+			"2",
+			2,
+			2,
+		},
+		{
+			"10",
+			10,
+			4,
+		},
+		{
+			"28",
+			28,
+			6,
+		},
+		{
+			"76576500",
+			76576500,
+			576,
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			got := Tau(tc.input)
+			if got != tc.want {
+				t.Errorf("Tau(%d)=%d, want %d", tc.input, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestGetTriangularNumber(t *testing.T) {
+	tt := []struct {
+		name  string
+		count int
+		want  int
+	}{
+		{
+			"1",
+			1,
+			1,
+		},
+		{
+			"2",
+			2,
+			3,
+		},
+		{
+			"7",
+			7,
+			28,
+		},
+		{
+			"10",
+			10,
+			55,
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			got := GetTriangularNumber(tc.count)
+			if !reflect.DeepEqual(got, tc.want) {
+				t.Errorf("GetTriangularNumber(%d)=%v, want %v", tc.count, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestListDivisors(t *testing.T) {
+	tt := []struct {
+		name  string
+		input int
+		want  []int
+	}{
+		{
+			"1",
+			1,
+			[]int{1},
+		},
+		{
+			"3",
+			3,
+			[]int{1, 3},
+		},
+		{
+			"6",
+			6,
+			[]int{1, 2, 3, 6},
+		},
+		{
+			"28",
+			28,
+			[]int{1, 2, 4, 7, 14, 28},
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			got := ListDivisors(tc.input)
+			if !reflect.DeepEqual(got, tc.want) {
+				t.Errorf("ListDivisors(%d)=%v, want %v", tc.input, got, tc.want)
+			}
+		})
+	}
+}