Add solution and test-cases for problem 2938

leetcode/2901-3000/2938.Separate-Black-and-White-Balls/README.md

@@ -1,28 +1,42 @@
 # [2938.Separate Black and White Balls][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
+There are `n` balls on a table, each ball has a color black or white.
+
+You are given a **0-indexed** binary string `s` of length `n`, where `1` and `0` represent black and white balls, respectively.
+
+In each step, you can choose two adjacent balls and swap them.
+
+Return the **minimum** number of steps to group all the black balls to the right and all the white balls to the left.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: s = "101"
+Output: 1
+Explanation: We can group all the black balls to the right in the following way:
+- Swap s[0] and s[1], s = "011".
+Initially, 1s are not grouped together, requiring at least 1 step to group them to the right.
 ```
 
-## 题意
-> ...
-
-## 题解
+**Example 2:**
 
-### 思路1
-> ...
-Separate Black and White Balls
-```go
 ```
+Input: s = "100"
+Output: 2
+Explanation: We can group all the black balls to the right in the following way:
+- Swap s[0] and s[1], s = "010".
+- Swap s[1] and s[2], s = "001".
+It can be proven that the minimum number of steps needed is 2.
+```
+
+**Example 3:**
 
+```
+Input: s = "0111"
+Output: 0
+Explanation: All the black balls are already grouped to the right.
+```
 
 ## 结语
 

leetcode/2901-3000/2938.Separate-Black-and-White-Balls/Solution.go

@@ -1,5 +1,13 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(s string) int64 {
+	index := -1
+	dis := int64(0)
+	for i := range s {
+		if s[i] == '0' {
+			index++
+			dis += int64(i - index)
+		}
+	}
+	return dis
 }

leetcode/2901-3000/2938.Separate-Black-and-White-Balls/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", "101", 1},
+		{"TestCase2", "100", 2},
+		{"TestCase3", "0111", 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() {
 }