Merge pull request #1383 from 0xff-dev/3381

Add solution and test-cases for problem 3381

Author: 6boris

leetcode/3301-3400/3381.Maximum-Subarray-Sum-With-Length-Divisible-by-K/README.md

@@ -1,28 +1,45 @@
 # [3381.Maximum Subarray Sum With Length Divisible by K][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 array of integers `nums` and an integer `k`.
+
+Return the **maximum** sum of a subarray of `nums`, such that the size of the subarray is **divisible** by `k`.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: nums = [1,2], k = 1
+
+Output: 3
+
+Explanation:
+
+The subarray [1, 2] with sum 3 has length equal to 2 which is divisible by 1.
+```
+
+**Example 2:**
+
 ```
+Input: nums = [-1,-2,-3,-4,-5], k = 4
+
+Output: -10
 
-## 题意
-> ...
+Explanation:
+
+The maximum sum subarray is [-1, -2, -3, -4] which has length equal to 4 which is divisible by 4.
+```
 
-## 题解
+**Example 3:**
 
-### 思路1
-> ...
-Maximum Subarray Sum With Length Divisible by K
-```go
 ```
+Input: nums = [-5,1,2,-3,4], k = 2
 
+Output: 4
+
+Explanation:
+
+The maximum sum subarray is [1, 2, -3, 4] which has length equal to 4 which is divisible by 2.
+```
 
 ## 结语
 

leetcode/3301-3400/3381.Maximum-Subarray-Sum-With-Length-Divisible-by-K/Solution.go

@@ -1,5 +1,24 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import "math"
+
+func Solution(nums []int, k int) int64 {
+	n := len(nums)
+	prefixSum := int64(0)
+	maxSum := int64(math.MinInt64)
+	kSum := make([]int64, k)
+	for i := range k {
+		kSum[i] = math.MaxInt64 / 2
+	}
+	kSum[k-1] = 0
+	for i := range n {
+		prefixSum += int64(nums[i])
+		if prefixSum-kSum[i%k] > maxSum {
+			maxSum = prefixSum - kSum[i%k]
+		}
+		if prefixSum < kSum[i%k] {
+			kSum[i%k] = prefixSum
+		}
+	}
+	return maxSum
 }

leetcode/3301-3400/3381.Maximum-Subarray-Sum-With-Length-Divisible-by-K/Solution_test.go

@@ -10,30 +10,31 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs []int
+		k      int
+		expect int64
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", []int{1, 2}, 1, 3},
+		{"TestCase2", []int{-1, -2, -3, -4, -5}, 4, -10},
+		{"TestCase3", []int{-5, 1, 2, -3, 4}, 2, 4},
 	}
 
 	//	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.inputs, c.k)
 			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",
+					c.expect, got, c.inputs, c.k)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }