Add solution and test-cases for problem 1915

Author: 0xff-dev

leetcode/1901-2000/1915.Number-of-Wonderful-Substrings/README.md

@@ -1,28 +1,52 @@
 # [1915.Number of Wonderful Substrings][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
+A **wonderful** string is a string where **at most one** letter appears an **odd** number of times.
+
+- For example, `"ccjjc"` and `"abab"` are wonderful, but `"ab"` is not.
+
+Given a string `word` that consists of the first ten lowercase English letters (`'a'` through `'j'`), return the **number of wonderful non-empty substrings** in `word`. If the same substring appears multiple times in word, then count **each occurrence** separately.
+
+A **substring** is a contiguous sequence of characters in a string.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: word = "aba"
+Output: 4
+Explanation: The four wonderful substrings are underlined below:
+- "aba" -> "a"
+- "aba" -> "b"
+- "aba" -> "a"
+- "aba" -> "aba"
 ```
 
-## 题意
-> ...
-
-## 题解
+**Example 2:**
 
-### 思路1
-> ...
-Number of Wonderful Substrings
-```go
 ```
+Input: word = "aabb"
+Output: 9
+Explanation: The nine wonderful substrings are underlined below:
+- "aabb" -> "a"
+- "aabb" -> "aa"
+- "aabb" -> "aab"
+- "aabb" -> "aabb"
+- "aabb" -> "a"
+- "aabb" -> "abb"
+- "aabb" -> "b"
+- "aabb" -> "bb"
+- "aabb" -> "b"
+```
+
+**Example 3:**
 
+```
+Input: word = "he"
+Output: 2
+Explanation: The two wonderful substrings are underlined below:
+- "he" -> "h"
+- "he" -> "e"
+```
 
 ## 结语
 

leetcode/1901-2000/1915.Number-of-Wonderful-Substrings/Solution.go

@@ -1,5 +1,20 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(word string) int64 {
+	// 10bit
+	ans := int64(0)
+	l := len(word)
+	state := make(map[int]int64)
+	state[0] = 1
+	mask := 0
+	for i := 0; i < l; i++ {
+		mask ^= (1 << int(word[i]-'a'))
+		c := state[mask]
+		ans += c
+		state[mask] = c + 1
+		for i := 0; i < 10; i++ {
+			ans += state[mask^(1<<i)]
+		}
+	}
+	return ans
 }

leetcode/1901-2000/1915.Number-of-Wonderful-Substrings/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 string
+		expect int64
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", "aba", 4},
+		{"TestCase2", "aabb", 9},
+		{"TestCase3", "he", 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() {
 }