Add solution and test-cases for problem 2106

leetcode/2101-2200/2106.Maximum-Fruits-Harvested-After-at-Most-K-Steps/README.md

@@ -1,28 +1,53 @@
 # [2106.Maximum Fruits Harvested After at Most K Steps][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
+Fruits are available at some positions on an infinite x-axis. You are given a 2D integer array `fruits` where `fruits[i] = [positioni, amounti]` depicts `amounti` fruits at the position `positioni`. `fruits` is already **sorted** by `positioni` in **ascending order**, and each `positioni` is **unique**.
+
+You are also given an integer `startPos` and an integer `k`. Initially, you are at the position `startPos`. From any position, you can either walk to the **left or right**. It takes **one step** to move **one unit** on the x-axis, and you can walk **at most** `k` steps in total. For every position you reach, you harvest all the fruits at that position, and the fruits will disappear from that position.
+
+Return the **maximum total number** of fruits you can harvest.
 
-**Example 1:**
+**Example 1:**  
+
+![1](./1.png)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: fruits = [[2,8],[6,3],[8,6]], startPos = 5, k = 4
+Output: 9
+Explanation: 
+The optimal way is to:
+- Move right to position 6 and harvest 3 fruits
+- Move right to position 8 and harvest 6 fruits
+You moved 3 steps and harvested 3 + 6 = 9 fruits in total.
 ```
 
-## 题意
-> ...
+**Example 2:**  
 
-## 题解
+![2](./2.png)
 
-### 思路1
-> ...
-Maximum Fruits Harvested After at Most K Steps
-```go
+```
+Input: fruits = [[0,9],[4,1],[5,7],[6,2],[7,4],[10,9]], startPos = 5, k = 4
+Output: 14
+Explanation: 
+You can move at most k = 4 steps, so you cannot reach position 0 nor 10.
+The optimal way is to:
+- Harvest the 7 fruits at the starting position 5
+- Move left to position 4 and harvest 1 fruit
+- Move right to position 6 and harvest 2 fruits
+- Move right to position 7 and harvest 4 fruits
+You moved 1 + 3 = 4 steps and harvested 7 + 1 + 2 + 4 = 14 fruits in total.
 ```
 
+**Example 3:**  
+
+![3](./3.png)
+
+```
+Input: fruits = [[0,3],[6,4],[8,5]], startPos = 3, k = 2
+Output: 0
+Explanation:
+You can move at most k = 2 steps and cannot reach any position with fruits.
+```
 
 ## 结语
 

leetcode/2101-2200/2106.Maximum-Fruits-Harvested-After-at-Most-K-Steps/Solution.go

@@ -1,5 +1,57 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import "sort"
+
+func Solution(fruits [][]int, startPos int, k int) int {
+	l := len(fruits)
+	index := sort.Search(l, func(i int) bool {
+		return fruits[i][0] >= startPos
+	})
+	ans, dis := 0, 0
+	sum := make([]int, l)
+
+	a := 0
+	for i := index; i < l; i++ {
+		a += fruits[i][1]
+		sum[i] = a
+	}
+	a = 0
+	for i := index - 1; i >= 0; i-- {
+		a += fruits[i][1]
+		sum[i] = a
+	}
+	right := 0
+	for i := index; i < l; i++ {
+		dis = fruits[i][0] - startPos
+		if dis > k {
+			break
+		}
+		right += fruits[i][1]
+		ans = max(ans, right)
+
+		if x := sort.Search(index, func(j int) bool {
+			return fruits[i][0]-fruits[j][0] <= k-dis
+		}); x != index {
+			ans = max(ans, right+sum[x])
+		}
+	}
+	left := 0
+	ll := l - index
+
+	for i := index - 1; i >= 0; i-- {
+		dis = startPos - fruits[i][0]
+		if dis > k {
+			break
+		}
+		left += fruits[i][1]
+
+		ans = max(ans, left)
+		if x := sort.Search(ll, func(j int) bool {
+			return fruits[index+j][0]-fruits[i][0] > k-dis
+		}); x != 0 {
+			ans = max(ans, left+sum[index+x-1])
+
+		}
+	}
+	return ans
 }

leetcode/2101-2200/2106.Maximum-Fruits-Harvested-After-at-Most-K-Steps/Solution_test.go

@@ -9,31 +9,32 @@ import (
 func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
-		name   string
-		inputs bool
-		expect bool
+		name        string
+		inputs      [][]int
+		startPos, k int
+		expect      int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", [][]int{{2, 8}, {6, 3}, {8, 6}}, 5, 4, 9},
+		{"TestCase2", [][]int{{0, 9}, {4, 1}, {5, 7}, {6, 2}, {7, 4}, {10, 9}}, 5, 4, 14},
+		{"TestCase3", [][]int{{0, 3}, {6, 4}, {8, 5}}, 3, 2, 0},
 	}
 
 	//	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.startPos, 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 %v",
+					c.expect, got, c.inputs, c.startPos, 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() {
 }