Add solution and test-cases for problem 3042

leetcode/3001-3100/3042.Count-Prefix-and-Suffix-Pairs-I/README.md

@@ -1,28 +1,48 @@
 # [3042.Count Prefix and Suffix Pairs 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 a **0-indexed** string array `words`.
+
+Let's define a **boolean** function `isPrefixAndSuffix` that takes two strings, `str1` and `str2`:
+
+- `isPrefixAndSuffix(str1, str2)` returns `true` if `str1` is **both** a `prefix` and a `suffix` of `str2`, and `false` otherwise.
+
+For example, `isPrefixAndSuffix("aba", "ababa")` is `true` because `"aba"` is a prefix of `"ababa"` and also a suffix, but `isPrefixAndSuffix("abc", "abcd")` is `false`.
+
+Return an integer denoting the **number** of index pairs `(i, j)` such that `i < j`, and `isPrefixAndSuffix(words[i], words[j])` is `true`.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: words = ["a","aba","ababa","aa"]
+Output: 4
+Explanation: In this example, the counted index pairs are:
+i = 0 and j = 1 because isPrefixAndSuffix("a", "aba") is true.
+i = 0 and j = 2 because isPrefixAndSuffix("a", "ababa") is true.
+i = 0 and j = 3 because isPrefixAndSuffix("a", "aa") is true.
+i = 1 and j = 2 because isPrefixAndSuffix("aba", "ababa") is true.
+Therefore, the answer is 4.
 ```
 
-## 题意
-> ...
+**Example 2:**
 
-## 题解
-
-### 思路1
-> ...
-Count Prefix and Suffix Pairs I
-```go
 ```
+Input: words = ["pa","papa","ma","mama"]
+Output: 2
+Explanation: In this example, the counted index pairs are:
+i = 0 and j = 1 because isPrefixAndSuffix("pa", "papa") is true.
+i = 2 and j = 3 because isPrefixAndSuffix("ma", "mama") is true.
+Therefore, the answer is 2.
+```
+
+**Example 3:**
 
+```
+Input: words = ["abab","ab"]
+Output: 0
+Explanation: In this example, the only valid index pair is i = 0 and j = 1, and isPrefixAndSuffix("abab", "ab") is false.
+Therefore, the answer is 0.
+```
 
 ## 结语
 

leetcode/3001-3100/3042.Count-Prefix-and-Suffix-Pairs-I/Solution.go

@@ -1,5 +1,15 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import "strings"
+
+func Solution(words []string) int {
+	ans := 0
+	for i := 0; i < len(words); i++ {
+		for j := i + 1; j < len(words); j++ {
+			if strings.HasPrefix(words[j], words[i]) && strings.HasSuffix(words[j], words[i]) {
+				ans++
+			}
+		}
+	}
+	return ans
 }

leetcode/3001-3100/3042.Count-Prefix-and-Suffix-Pairs-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 []string
+		expect int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", []string{"a", "aba", "ababa", "aa"}, 4},
+		{"TestCase2", []string{"pa", "papa", "ma", "mama"}, 2},
+		{"TestCase3", []string{"abab", "ab"}, 0},
 	}
 
 	//	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() {
 }