From 1d954c8d7719e0fc6e2af87f03cc34d0f94b8cdd Mon Sep 17 00:00:00 2001
From: VicRen <vic.ren@me.com>
Date: Fri, 30 Oct 2020 12:28:47 +0800
Subject: [PATCH] 30: digit fifth powers

---
 30_digit_fifth_powers/main.go      | 32 ++++++++++++
 30_digit_fifth_powers/main_test.go | 78 ++++++++++++++++++++++++++++++
 2 files changed, 110 insertions(+)
 create mode 100644 30_digit_fifth_powers/main.go
 create mode 100644 30_digit_fifth_powers/main_test.go

diff --git a/30_digit_fifth_powers/main.go b/30_digit_fifth_powers/main.go
new file mode 100644
index 0000000..77f06f8
--- /dev/null
+++ b/30_digit_fifth_powers/main.go
@@ -0,0 +1,32 @@
+package main
+
+import "fmt"
+
+func main() {
+	sum := 0
+	for i := 2; i < 355000; i++ {
+		if sumOfFifthPowerOfDigits(i) == int64(i) {
+			sum += i
+		}
+	}
+	fmt.Println(sum)
+}
+
+func sumOfFifthPowerOfDigits(n int) int64 {
+	number := n
+	sum := int64(0)
+	for number > 0 {
+		x := number % 10
+		sum += fifthPower(x)
+		number /= 10
+	}
+	return sum
+}
+
+func fifthPower(n int) int64 {
+	p := int64(1)
+	for i := 0; i < 5; i++ {
+		p *= int64(n)
+	}
+	return p
+}
diff --git a/30_digit_fifth_powers/main_test.go b/30_digit_fifth_powers/main_test.go
new file mode 100644
index 0000000..5c6a731
--- /dev/null
+++ b/30_digit_fifth_powers/main_test.go
@@ -0,0 +1,78 @@
+package main
+
+import (
+	"testing"
+)
+
+func Test_fifthPower(t *testing.T) {
+	type args struct {
+		n int
+	}
+	tests := []struct {
+		name string
+		args args
+		want int64
+	}{
+		{
+			"1",
+			args{1},
+			1,
+		},
+		{
+			"2",
+			args{2},
+			32,
+		},
+		{
+			"9",
+			args{9},
+			59049,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := fifthPower(tt.args.n); got != tt.want {
+				t.Errorf("fifthPower() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_sumOfFifthPowerOfDigits(t *testing.T) {
+	type args struct {
+		n int
+	}
+	tests := []struct {
+		name string
+		args args
+		want int64
+	}{
+		{
+			"1",
+			args{1},
+			1,
+		},
+		{
+			"11",
+			args{11},
+			2,
+		},
+		{
+			"111",
+			args{111},
+			3,
+		},
+		{
+			"222",
+			args{222},
+			96,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := sumOfFifthPowerOfDigits(tt.args.n); got != tt.want {
+				t.Errorf("sumOfFifthPowerOfDigits() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}