From f060af2b7d4beb9249de8bc0add72042578a3f7c Mon Sep 17 00:00:00 2001
From: kercylan98 <kercylan@gmail.com>
Date: Mon, 4 Dec 2023 14:00:30 +0800
Subject: [PATCH] =?UTF-8?q?feat:=20maths=20=E6=96=B0=E5=A2=9E=20MakeLastDi?=
 =?UTF-8?q?gitsZero=20=E5=87=BD=E6=95=B0=EF=BC=8C=E7=94=A8=E4=BA=8E?=
 =?UTF-8?q?=E5=B0=86=E4=BC=A0=E5=85=A5=E6=95=B0=E5=AD=97=E7=9A=84=E6=9C=AB?=
 =?UTF-8?q?=E4=BD=8D=20n=20=E4=BD=8D=E8=AE=BE=E7=BD=AE=E4=B8=BA=200?=
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---
 utils/maths/math.go      | 11 +++++++++++
 utils/maths/math_test.go | 14 ++++++++++++++
 utils/random/number.go   |  9 +++++++++
 3 files changed, 34 insertions(+)
 create mode 100644 utils/maths/math_test.go

diff --git a/utils/maths/math.go b/utils/maths/math.go
index 441f23c..6166c87 100644
--- a/utils/maths/math.go
+++ b/utils/maths/math.go
@@ -204,3 +204,14 @@ func IsOdd[V generic.Integer](n V) bool {
 func IsEven[V generic.Integer](n V) bool {
 	return 0 == (int64(n) & 1)
 }
+
+// MakeLastDigitsZero 返回一个新的数，其中 num 的最后 digits 位数被设为零。
+//   - 函数首先创建一个 10 的 digits 次方的遮罩，然后通过整除和乘以这个遮罩来使 num 的最后 digits 位归零。
+//   - 当 T 类型为浮点型时，将被向下取整后再进行转换
+func MakeLastDigitsZero[T generic.Number](num T, digits int) T {
+	var mask int64 = 1
+	for i := 0; i < digits; i++ {
+		mask *= 10
+	}
+	return T(int64(num) / mask * mask)
+}
diff --git a/utils/maths/math_test.go b/utils/maths/math_test.go
new file mode 100644
index 0000000..1e2893d
--- /dev/null
+++ b/utils/maths/math_test.go
@@ -0,0 +1,14 @@
+package maths_test
+
+import (
+	"github.com/kercylan98/minotaur/utils/maths"
+	"github.com/kercylan98/minotaur/utils/random"
+	"testing"
+)
+
+func TestMakeLastDigitsZero(t *testing.T) {
+	for i := 0; i < 20; i++ {
+		n := float64(random.Int64(100, 999999))
+		t.Log(n, 3, maths.MakeLastDigitsZero(n, 3))
+	}
+}
diff --git a/utils/random/number.go b/utils/random/number.go
index fd9c54b..2a42e4a 100644
--- a/utils/random/number.go
+++ b/utils/random/number.go
@@ -7,16 +7,25 @@ import (
 
 // Int64 返回一个介于min和max之间的int64类型的随机数。
 func Int64(min int64, max int64) int64 {
+	if min == max {
+		return min
+	}
 	return min + rand.Int63n(max+1-min)
 }
 
 // Int 返回一个介于min和max之间的的int类型的随机数。
 func Int(min int, max int) int {
+	if min == max {
+		return min
+	}
 	return int(Int64(int64(min), int64(max)))
 }
 
 // Duration 返回一个介于min和max之间的的Duration类型的随机数。
 func Duration(min int64, max int64) time.Duration {
+	if min == max {
+		return time.Duration(min)
+	}
 	return time.Duration(Int64(min, max))
 }