Add solution and test-cases for problem 2240

Author: 0xff-dev

leetcode/2201-2300/2240.Number-of-Ways-to-Buy-Pens-and-Pencils/README.md

@@ -1,28 +1,30 @@
 # [2240.Number of Ways to Buy Pens and Pencils][title]
 
-> [!WARNING|style:flat]
-> This question is temporarily unanswered if you have good ideas. Welcome to [Create Pull Request PR](https://github.com/kylesliu/awesome-golang-algorithm)
-
 ## Description
 
+You are given an integer `total` indicating the amount of money you have. You are also given two integers `cost1` and `cost2` indicating the price of a pen and pencil respectively. You can spend **part or all** of your money to buy multiple quantities (or none) of each kind of writing utensil.
+
+Return the **number of distinct ways** you can buy some number of pens and pencils.
+
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: total = 20, cost1 = 10, cost2 = 5
+Output: 9
+Explanation: The price of a pen is 10 and the price of a pencil is 5.
+- If you buy 0 pens, you can buy 0, 1, 2, 3, or 4 pencils.
+- If you buy 1 pen, you can buy 0, 1, or 2 pencils.
+- If you buy 2 pens, you cannot buy any pencils.
+The total number of ways to buy pens and pencils is 5 + 3 + 1 = 9.
 ```
 
-## 题意
-> ...
+**Example 2:**
 
-## 题解
-
-### 思路1
-> ...
-Number of Ways to Buy Pens and Pencils
-```go
 ```
-
+Input: total = 5, cost1 = 10, cost2 = 10
+Output: 1
+Explanation: The price of both pens and pencils are 10, which cost more than total, so you cannot buy any writing utensils. Therefore, there is only 1 way: buy 0 pens and 0 pencils.
+```
 
 ## 结语
 

leetcode/2201-2300/2240.Number-of-Ways-to-Buy-Pens-and-Pencils/Solution.go

@@ -1,5 +1,11 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(total int, cost1 int, cost2 int) int64 {
+	var ret int64
+	penCount := 0
+	for ; penCount*cost1 <= total; penCount++ {
+		left := (total-penCount*cost1)/cost2 + 1 // 0
+		ret += int64(left)
+	}
+	return ret
 }

leetcode/2201-2300/2240.Number-of-Ways-to-Buy-Pens-and-Pencils/Solution_test.go

@@ -9,31 +9,30 @@ import (
 func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
-		name   string
-		inputs bool
-		expect bool
+		name                string
+		total, cost1, cost2 int
+		expect              int64
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", 20, 10, 5, 9},
+		{"TestCase2", 5, 10, 10, 1},
 	}
 
 	//	开始测试
 	for i, c := range cases {
 		t.Run(c.name+" "+strconv.Itoa(i), func(t *testing.T) {
-			got := Solution(c.inputs)
+			got := Solution(c.total, c.cost1, c.cost2)
 			if !reflect.DeepEqual(got, c.expect) {
-				t.Fatalf("expected: %v, but got: %v, with inputs: %v",
-					c.expect, got, c.inputs)
+				t.Fatalf("expected: %v, but got: %v, with inputs: %v %v %v",
+					c.expect, got, c.total, c.cost1, c.cost2)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }