Add solution and test-cases for problem 3583

Author: 0xff-dev

leetcode/3501-3600/3583.Count-Special-Triplets/README.md

@@ -1,28 +1,70 @@
 # [3583.Count Special Triplets][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 **special triplet** is defined as a triplet of indices `(i, j, k)` such that:
+
+- `0 <= i < j < k < n`, where `n = nums.length`
+- `nums[i] == nums[j] * 2`
+- `nums[k] == nums[j] * 2`
+
+Return the total number of **special triplets** in the array.
+
+Since the answer may be large, return it **modulo** `10^9 + 7`.
 
 **Example 1:**
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: nums = [6,3,6]
+
+Output: 1
+
+Explanation:
+
+The only special triplet is (i, j, k) = (0, 1, 2), where:
+
+nums[0] = 6, nums[1] = 3, nums[2] = 6
+nums[0] = nums[1] * 2 = 3 * 2 = 6
+nums[2] = nums[1] * 2 = 3 * 2 = 6
+```
+
+**Example 2:**
+
 ```
+Input: nums = [0,1,0,0]
+
+Output: 1
+
+Explanation:
+
+The only special triplet is (i, j, k) = (0, 2, 3), where:
 
-## 题意
-> ...
+nums[0] = 0, nums[2] = 0, nums[3] = 0
+nums[0] = nums[2] * 2 = 0 * 2 = 0
+nums[3] = nums[2] * 2 = 0 * 2 = 0
+```
 
-## 题解
+**Example 3:**
 
-### 思路1
-> ...
-Count Special Triplets
-```go
 ```
+Input: nums = [8,4,2,8,4]
+
+Output: 2
+
+Explanation:
 
+There are exactly two special triplets:
+
+(i, j, k) = (0, 1, 3)
+nums[0] = 8, nums[1] = 4, nums[3] = 8
+nums[0] = nums[1] * 2 = 4 * 2 = 8
+nums[3] = nums[1] * 2 = 4 * 2 = 8
+(i, j, k) = (1, 2, 4)
+nums[1] = 4, nums[2] = 2, nums[4] = 4
+nums[1] = nums[2] * 2 = 2 * 2 = 4
+nums[4] = nums[2] * 2 = 2 * 2 = 4
+```
 
 ## 结语
 

leetcode/3501-3600/3583.Count-Special-Triplets/Solution.go

@@ -1,5 +1,23 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(nums []int) int {
+	const MOD = 1000000007
+	numCnt := make(map[int]int)
+	numPartialCnt := make(map[int]int)
+
+	for _, v := range nums {
+		numCnt[v]++
+	}
+
+	ans := 0
+	for _, v := range nums {
+		target := v * 2
+		lCnt := numPartialCnt[target]
+		numPartialCnt[v]++
+		rCnt := numCnt[target] - numPartialCnt[target]
+
+		ans = (ans + lCnt*rCnt) % MOD
+	}
+
+	return ans
 }

leetcode/3501-3600/3583.Count-Special-Triplets/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{6, 3, 6}, 1},
+		{"TestCase2", []int{0, 1, 0, 0}, 1},
+		{"TestCase3", []int{8, 4, 2, 8, 4}, 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() {
 }