Add solution and test-cases for problem 1220

leetcode/1201-1300/1220.Count-Vowels-Permutation/README.md

@@ -1,28 +1,39 @@
 # [1220.Count Vowels Permutation][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
+Given an integer `n`, your task is to count how many strings of length `n` can be formed under the following rules:
+
+- Each character is a lower case vowel (`'a'`, `'e'`, `'i'`, `'o'`, `'u'`)
+- Each vowel `'a'` may only be followed by an `'e'`.
+- Each vowel `'e'` may only be followed by an `'a'` or an `'i'`.
+- Each vowel `'i'` **may not** be followed by another `'i'`.
+- Each vowel `'o'` may only be followed by an `'i'` or a `'u'`.
+- Each vowel `'u'` may only be followed by an `'a'`.
+
+Since the answer may be too large, return it modulo `10^9 + 7`.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: n = 1
+Output: 5
+Explanation: All possible strings are: "a", "e", "i" , "o" and "u".
 ```
 
-## 题意
-> ...
-
-## 题解
+**Example 2:**
 
-### 思路1
-> ...
-Count Vowels Permutation
-```go
 ```
+Input: n = 2
+Output: 10
+Explanation: All possible strings are: "ae", "ea", "ei", "ia", "ie", "io", "iu", "oi", "ou" and "ua".
+```
+
+**Example 3:**
 
+```
+Input: n = 5
+Output: 68
+```
 
 ## 结语
 

leetcode/1201-1300/1220.Count-Vowels-Permutation/Solution.go

@@ -1,5 +1,26 @@
 package Solution
 
-func Solution(x bool) bool {
-return x
+const mod1220 = 1000000007
+
+// 类似黑白房那个问题
+// 结尾两个是黑只能接白的那种感觉 dp 确定是如何结尾的
+
+func Solution(n int) int {
+a, e, i, o, u := 1, 1, 1, 1, 1
+
+//	'a': {'e'},
+//	'e': {'a', 'i'},
+//	'i': {'a', 'e', 'o', 'u'},
+//	'o': {'i', 'u'},
+//	'u': {'a'},
+for idx := 2; idx <= n; idx++ {
+// e, i, u后面可以接a
+a1 := (e + i + u) % mod1220 // x
+e1 := (a + i) % mod1220 //
+i1 := (e + o) % mod1220 //
+o1 := i % mod1220
+u1 := (i + o) % mod1220
+a, e, i, o, u = a1, e1, i1, o1, u1
+}
+return (a + e + i + o + u) % mod1220
 }

leetcode/1201-1300/1220.Count-Vowels-Permutation/Solution_test.go

@@ -10,12 +10,14 @@ 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", 1, 5},
+{"TestCase2", 10, 1739},
+{"TestCase3", 100, 173981881},
+{"TestCase4", 1000, 89945857},
+{"TestCase5", 1798, 324384432},
 }
 
 //	开始测试