From 38ec5384fa3138a3b8f91109280ac90e18c2395a Mon Sep 17 00:00:00 2001
From: VicRen <vic.ren@me.com>
Date: Sat, 3 Oct 2020 22:25:38 +0800
Subject: [PATCH] largest palindrome product

---
 largest_palindrome_product/main.go            | 34 +++++++++++++
 largest_palindrome_product/palindrome_test.go | 48 +++++++++++++++++++
 2 files changed, 82 insertions(+)
 create mode 100644 largest_palindrome_product/main.go
 create mode 100644 largest_palindrome_product/palindrome_test.go

diff --git a/largest_palindrome_product/main.go b/largest_palindrome_product/main.go
new file mode 100644
index 0000000..2491f3d
--- /dev/null
+++ b/largest_palindrome_product/main.go
@@ -0,0 +1,34 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	var n int
+	var x int
+	var y int
+	for i := 100; i < 1000; i++ {
+		for j := 100; j < 1000; j++ {
+			tmp := i * j
+			if tmp > n && IsPalindrome(tmp) {
+				x = i
+				y = j
+				n = tmp
+			}
+		}
+	}
+	fmt.Println(x, y, n)
+}
+
+func IsPalindrome(n int) bool {
+	str := strconv.Itoa(n)
+	pb := strings.Builder{}
+	for i := len(str); i > 0; i-- {
+		pb.WriteString(str[i-1 : i])
+	}
+	pstr := pb.String()
+	return str == pstr
+}
diff --git a/largest_palindrome_product/palindrome_test.go b/largest_palindrome_product/palindrome_test.go
new file mode 100644
index 0000000..e276089
--- /dev/null
+++ b/largest_palindrome_product/palindrome_test.go
@@ -0,0 +1,48 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestIsPalindrome(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 := IsPalindrome(tc.input)
+			if got != tc.want {
+				t.Errorf("IsPalindrome(%d)=%v, want %v", tc.input, got, tc.want)
+			}
+		})
+	}
+}