Merge pull request #1261 from 0xff-dev/3201

Add solution and test-cases for problem 3201

Author: 6boris

leetcode/3201-3300/3201.Find-the-Maximum-Length-of-Valid-Subsequence-I/README.md

@@ -1,28 +1,50 @@
 # [3201.Find the Maximum Length of Valid Subsequence I][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 array `nums`.
+A `subsequence` `sub` of `nums` with length `x` is called **valid** if it satisfies:
+
+- `(sub[0] + sub[1]) % 2 == (sub[1] + sub[2]) % 2 == ... == (sub[x - 2] + sub[x - 1]) % 2`.
+
+Return the length of the **longest valid** subsequence of `nums`.
+
+A **subsequence** is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: nums = [1,2,3,4]
+
+Output: 4
+
+Explanation:
+
+The longest valid subsequence is [1, 2, 3, 4].
+```
+
+**Example 2:**
+
 ```
+Input: nums = [1,2,1,1,2,1,2]
+
+Output: 6
+
+Explanation:
 
-## 题意
-> ...
+The longest valid subsequence is [1, 2, 1, 2, 1, 2].
+```
 
-## 题解
+**Example 3:**
 
-### 思路1
-> ...
-Find the Maximum Length of Valid Subsequence I
-```go
 ```
+Input: nums = [1,3]
+
+Output: 2
 
+Explanation:
+
+The longest valid subsequence is [1, 3].
+```
 
 ## 结语
 

leetcode/3201-3300/3201.Find-the-Maximum-Length-of-Valid-Subsequence-I/Solution.go

@@ -1,5 +1,24 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(nums []int) int {
+	// 要么一连串偶数(奇数)，可以保证%2都是0
+	a, b := 0, 0
+	for _, n := range nums {
+		if n&1 == 0 {
+			a++
+			continue
+		}
+		b++
+	}
+	ans := max(a, b)
+	// 开始找一个奇数一个偶数, 保证了结果一定是奇数
+	evenLen, oddLen := 0, 0
+	for _, n := range nums {
+		if n&1 == 0 {
+			evenLen = oddLen + 1
+			continue
+		}
+		oddLen = evenLen + 1
+	}
+	return max(ans, oddLen, evenLen)
 }

leetcode/3201-3300/3201.Find-the-Maximum-Length-of-Valid-Subsequence-I/Solution_test.go

@@ -10,12 +10,12 @@ 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, 2, 3, 4}, 4},
+		{"TestCase2", []int{1, 2, 1, 1, 2, 1, 2}, 6},
+		{"TestCase3", []int{1, 3}, 2},
 	}
 
 	//	开始测试
@@ -30,10 +30,10 @@ 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() {
 }