Add solution and test-cases for problem 1671

leetcode/1601-1700/1671.Minimum-Number-of-Removals-to-Make-Mountain-Array/README.md

@@ -1,28 +1,31 @@
 # [1671.Minimum Number of Removals to Make Mountain Array][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 may recall that an array `arr` is a **mountain array** if and only if:
+
+- `arr.length >= 3`
+- There exists some index `i` (**0-indexed**) with `0 < i < arr.length - 1` such that:
+
+    - `arr[0] < arr[1] < ... < arr[i - 1] < arr[i]`
+    - `arr[i] > arr[i + 1] > ... > arr[arr.length - 1]`
+
+Given an integer array `nums`, return the **minimum** number of elements to remove to make `nums` a **mountain array**.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: nums = [1,3,1]
+Output: 0
+Explanation: The array itself is a mountain array so we do not need to remove any elements.
 ```
 
-## 题意
-> ...
+**Example 2:**
 
-## 题解
-
-### 思路1
-> ...
-Minimum Number of Removals to Make Mountain Array
-```go
 ```
-
+Input: nums = [2,1,1,5,6,2,3,1]
+Output: 3
+Explanation: One solution is to remove the elements at indices 0, 1, and 5, making the array nums = [1,5,6,3,1].
+```
 
 ## 结语
 

leetcode/1601-1700/1671.Minimum-Number-of-Removals-to-Make-Mountain-Array/Solution.go

@@ -1,5 +1,36 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(nums []int) int {
+	l := len(nums)
+	if l < 3 {
+		return 0
+	}
+	left, right := make([]int, l), make([]int, l)
+	left[0] = 1
+	for i := 1; i < l; i++ {
+		left[i] = 1
+		for pre := i - 1; pre >= 0; pre-- {
+			if nums[pre] < nums[i] {
+				left[i] = max(left[i], left[pre]+1)
+			}
+		}
+	}
+	right[l-1] = 1
+	for i := l - 2; i >= 0; i-- {
+		right[i] = 1
+		for next := i + 1; next < l; next++ {
+			if nums[i] > nums[next] {
+				right[i] = max(right[i], right[next]+1)
+			}
+		}
+	}
+	ans := 0
+	for i := 1; i < l-1; i++ {
+		if left[i] == 1 || right[i] == 1 {
+			continue
+		}
+		now := left[i] + right[i] - 1
+		ans = max(ans, now)
+	}
+	return l - ans
 }

leetcode/1601-1700/1671.Minimum-Number-of-Removals-to-Make-Mountain-Array/Solution_test.go

@@ -10,12 +10,11 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs []int
+		expect int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", []int{1, 3, 1}, 0},
+		{"TestCase3", []int{2, 1, 1, 5, 6, 2, 3, 1}, 3},
 	}
 
 	//	开始测试
@@ -30,10 +29,10 @@ func TestSolution(t *testing.T) {
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }