Merge pull request #1182 from 0xff-dev/2145

Add solution and test-cases for problem 2145

Author: 6boris

leetcode/2101-2200/2145.Count-the-Hidden-Sequences/README.md

@@ -1,28 +1,49 @@
 # [2145.Count the Hidden Sequences][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 a **0-indexed** array of `n` integers `differences`, which describes the **differences** between each pair of **consecutive** integers of a **hidden** sequence of length `(n + 1)`. More formally, call the `hidden` sequence hidden, then we have that `differences[i] = hidden[i + 1] - hidden[i]`.
+
+You are further given two integers `lower` and `upper` that describe the **inclusive** range of values `[lower, upper]` that the hidden sequence can contain.
+
+- For example, given `differences = [1, -3, 4]`, `lower = 1`, `upper = 6`, the hidden sequence is a sequence of length `4` whose elements are in between `1` and `6` (**inclusive**).
+
+    - `[3, 4, 1, 5]` and `[4, 5, 2, 6]` are possible hidden sequences.
+    - `[5, 6, 3, 7]` is not possible since it contains an element greater than `6`.
+    - `[1, 2, 3, 4]` is not possible since the differences are not correct.
+
+Return the number of **possible** hidden sequences there are. If there are no possible sequences, return `0`.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: differences = [1,-3,4], lower = 1, upper = 6
+Output: 2
+Explanation: The possible hidden sequences are:
+- [3, 4, 1, 5]
+- [4, 5, 2, 6]
+Thus, we return 2.
 ```
 
-## 题意
-> ...
+**Example 2:**
 
-## 题解
-
-### 思路1
-> ...
-Count the Hidden Sequences
-```go
 ```
+Input: differences = [3,-4,5,1,-2], lower = -4, upper = 5
+Output: 4
+Explanation: The possible hidden sequences are:
+- [-3, 0, -4, 1, 2, 0]
+- [-2, 1, -3, 2, 3, 1]
+- [-1, 2, -2, 3, 4, 2]
+- [0, 3, -1, 4, 5, 3]
+Thus, we return 4.
+```
+
+**Example 3:**
 
+```
+Input: differences = [4,-7,2], lower = 3, upper = 6
+Output: 0
+Explanation: There are no possible hidden sequences. Thus, we return 0.
+```
 
 ## 结语
 

leetcode/2101-2200/2145.Count-the-Hidden-Sequences/Solution.go

@@ -1,5 +1,25 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import "math"
+
+func Solution(differences []int, lower int, upper int) int {
+	sum := int64(0)
+	var maxSum, minSum int64
+	maxSum, minSum = int64(0), math.MaxInt64
+	for _, n := range differences {
+		sum += int64(n)
+		maxSum = max(sum, maxSum)
+		minSum = min(sum, minSum)
+	}
+
+	ans := 0
+	il, ip := int64(lower), int64(upper)
+	for i := lower; i <= upper; i++ {
+		a := int64(i) + maxSum
+		b := int64(i) + minSum
+		if a >= il && a <= ip && b >= il && b <= ip {
+			ans++
+		}
+	}
+	return ans
 }

leetcode/2101-2200/2145.Count-the-Hidden-Sequences/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
+		differences  []int
+		lower, upper int
+		expect       int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", []int{1, -3, 4}, 1, 6, 2},
+		{"TestCase2", []int{3, -4, 5, 1, -2}, -4, 5, 4},
+		{"TestCase3", []int{4, -7, 2}, 3, 6, 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.differences, c.lower, c.upper)
 			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.differences, c.lower, c.upper)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }