From 3b69ef2618263005d0f6dcf618c4e99028bfeee1 Mon Sep 17 00:00:00 2001
From: VicRen <vic.ren@me.com>
Date: Fri, 6 Nov 2020 11:12:16 +0800
Subject: [PATCH] 36: double-base palindromes

---
 36_double_base_palindromes/main.go      |  42 ++++++++
 36_double_base_palindromes/main_test.go | 131 ++++++++++++++++++++++++
 2 files changed, 173 insertions(+)
 create mode 100644 36_double_base_palindromes/main.go
 create mode 100644 36_double_base_palindromes/main_test.go

diff --git a/36_double_base_palindromes/main.go b/36_double_base_palindromes/main.go
new file mode 100644
index 0000000..bdf51e1
--- /dev/null
+++ b/36_double_base_palindromes/main.go
@@ -0,0 +1,42 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	sum := 0
+	for i := 0; i < 1e6; i++ {
+		if isPalindromeDecimal(i) && isPalindromeString(convertToBinary(i)) {
+			sum += i
+		}
+	}
+	fmt.Println("sum:", sum)
+}
+
+func isPalindromeDecimal(n int) bool {
+	return isPalindromeString(strconv.Itoa(n))
+}
+
+func convertToBinary(num int) string {
+	s := ""
+	if num == 0 {
+		return "0"
+	}
+	for ; num > 0; num /= 2 {
+		lsb := num % 2
+		s = strconv.Itoa(lsb) + s
+	}
+	return s
+}
+
+func isPalindromeString(s string) bool {
+	pb := strings.Builder{}
+	for i := len(s); i > 0; i-- {
+		pb.WriteString(s[i-1 : i])
+	}
+	pstr := pb.String()
+	return s == pstr
+}
diff --git a/36_double_base_palindromes/main_test.go b/36_double_base_palindromes/main_test.go
new file mode 100644
index 0000000..4a643fb
--- /dev/null
+++ b/36_double_base_palindromes/main_test.go
@@ -0,0 +1,131 @@
+package main
+
+import (
+	"testing"
+)
+
+func Test_isPalindrome(t *testing.T) {
+	tt := []struct {
+		name  string
+		input int
+		want  bool
+	}{
+		{
+			"1",
+			1,
+			true,
+		},
+		{
+			"11",
+			11,
+			true,
+		},
+		{
+			"1001",
+			1001,
+			true,
+		},
+		{
+			"123456654321",
+			123456654321,
+			true,
+		},
+		{
+			"123456754321",
+			123456754321,
+			false,
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			got := isPalindromeDecimal(tc.input)
+			if got != tc.want {
+				t.Errorf("IsPalindrome(%d)=%v, want %v", tc.input, got, tc.want)
+			}
+		})
+	}
+}
+
+func Test_isPalindromeString(t *testing.T) {
+	type args struct {
+		s string
+	}
+	tests := []struct {
+		name string
+		args args
+		want bool
+	}{
+		{
+			"1",
+			args{"1"},
+			true,
+		},
+		{
+			"11",
+			args{"11"},
+			true,
+		},
+		{
+			"1001",
+			args{"1001"},
+			true,
+		},
+		{
+			"123456654321",
+			args{"123456654321"},
+			true,
+		},
+		{
+			"123456754321",
+			args{"123456754321"},
+			false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := isPalindromeString(tt.args.s); got != tt.want {
+				t.Errorf("isPalindromeString() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_convertToBinary(t *testing.T) {
+	type args struct {
+		num int
+	}
+	tests := []struct {
+		name string
+		args args
+		want string
+	}{
+		{
+			"1",
+			args{1},
+			"1",
+		},
+		{
+			"2",
+			args{2},
+			"10",
+		},
+		{
+			"3",
+			args{3},
+			"11",
+		},
+		{
+			"7",
+			args{7},
+			"111",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := convertToBinary(tt.args.num); got != tt.want {
+				t.Errorf("convertToBinary() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}