From acd90b8221320a64a380b815580b406ca1fd6d6b Mon Sep 17 00:00:00 2001
From: VicRen <vic.ren@me.com>
Date: Thu, 1 Oct 2020 15:09:06 +0800
Subject: [PATCH] Project Euler #2: Even Fibonacci numbers

---
 fibonacci/README.md         |  6 +++
 fibonacci/fibonacci_test.go | 77 +++++++++++++++++++++++++++++++++++++
 fibonacci/main.go           | 35 +++++++++++++++++
 3 files changed, 118 insertions(+)
 create mode 100644 fibonacci/README.md
 create mode 100644 fibonacci/fibonacci_test.go
 create mode 100644 fibonacci/main.go

diff --git a/fibonacci/README.md b/fibonacci/README.md
new file mode 100644
index 0000000..e10afe7
--- /dev/null
+++ b/fibonacci/README.md
@@ -0,0 +1,6 @@
+# Even Fibonacci numbers
+Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:
+
+1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
+
+By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.
\ No newline at end of file
diff --git a/fibonacci/fibonacci_test.go b/fibonacci/fibonacci_test.go
new file mode 100644
index 0000000..6d6b5b3
--- /dev/null
+++ b/fibonacci/fibonacci_test.go
@@ -0,0 +1,77 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestGetFibonacciTill(t *testing.T) {
+	tt := []struct {
+		name  string
+		input int
+		want  []int
+	}{
+		{
+			"till 1",
+			1,
+			[]int{1},
+		},
+		{
+			"till 2",
+			2,
+			[]int{1, 2},
+		},
+		{
+			"till 3",
+			3,
+			[]int{1, 2, 3},
+		},
+		{
+			"till 100",
+			100,
+			[]int{1, 2, 3, 5, 8, 13, 21, 34, 55, 89},
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			got := GetFibonacciTill(tc.input)
+			if !reflect.DeepEqual(got, tc.want) {
+				t.Errorf("GetFibonacciTill(%d)=%v, want %v", tc.input, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestIsEvenValue(t *testing.T) {
+	tt := []struct {
+		name  string
+		input int
+		want  bool
+	}{
+		{
+			"1",
+			1,
+			false,
+		},
+		{
+			"2",
+			2,
+			true,
+		},
+		{
+			"100",
+			100,
+			true,
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			got := IsEvenValue(tc.input)
+			if got != tc.want {
+				t.Errorf("IsEvenValue(%d)=%v, want %v", tc.input, got, tc.want)
+			}
+		})
+	}
+}
diff --git a/fibonacci/main.go b/fibonacci/main.go
new file mode 100644
index 0000000..6bf800d
--- /dev/null
+++ b/fibonacci/main.go
@@ -0,0 +1,35 @@
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	end := 4000000
+	nums := GetFibonacciTill(end)
+	fmt.Println("the fibonacci below 4000000 is", nums)
+	sum := 0
+	for _, n := range nums {
+		if IsEvenValue(n) {
+			sum += n
+		}
+	}
+	fmt.Println("event-value sum of numbers in 4000000 is", sum)
+}
+
+func GetFibonacciTill(n int) []int {
+	var ret []int
+	next := 1
+	last := 1
+	for next <= n {
+		add := next
+		ret = append(ret, add)
+		next += last
+		last = add
+	}
+	return ret
+}
+
+func IsEvenValue(n int) bool {
+	return n%2 == 0
+}