Add solution and test-cases for problem 3625

leetcode/3601-3700/3625.Count-Number-of-Trapezoids-II/README.md

@@ -1,15 +1,41 @@
 # [3625.Count Number of Trapezoids II][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 2D integer array `points` where `points[i] = [xi, yi]` represents the coordinates of the `ith` point on the Cartesian plane.
+
+Return the number of unique trapezoids that can be formed by choosing any four distinct points from `points`.
+
+A **trapezoid** is a convex quadrilateral with **at least one pair** of parallel sides. Two lines are parallel if and only if they have the same slope.
+
+**Example 1:**  
+
+![1](./1.png)
+
+```
+Input: points = [[-3,2],[3,0],[2,3],[3,2],[2,-3]]
+
+Output: 2
 
-**Example 1:**
+Explanation:
+
+There are two distinct ways to pick four points that form a trapezoid:
+
+The points [-3,2], [2,3], [3,2], [2,-3] form one trapezoid.
+The points [2,3], [3,2], [3,0], [2,-3] form another trapezoid.
+```
+
+**Example 2:**  
+
+![2](./2.png)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: points = [[0,0],[1,0],[0,1],[2,1]]
+
+Output: 1
+
+Explanation:
+
+There is only one trapezoid which can be formed.
 ```
 
 ## 题意

leetcode/3601-3700/3625.Count-Number-of-Trapezoids-II/Solution.go

@@ -1,5 +1,67 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(points [][]int) int {
+	n := len(points)
+	inf := 1e9 + 7
+	slopeToIntercept := make(map[float64][]float64)
+	midToSlope := make(map[float64][]float64)
+	ans := 0
+
+	for i := 0; i < n; i++ {
+		x1, y1 := points[i][0], points[i][1]
+		for j := i + 1; j < n; j++ {
+			x2, y2 := points[j][0], points[j][1]
+			dx := x1 - x2
+			dy := y1 - y2
+
+			var k, b float64
+			if x2 == x1 {
+				k = inf
+				b = float64(x1)
+			} else {
+				k = float64(y2-y1) / float64(x2-x1)
+				b = float64(y1*dx-x1*dy) / float64(dx)
+			}
+
+			mid := float64((x1+x2)*10000 + (y1 + y2))
+			slopeToIntercept[k] = append(slopeToIntercept[k], b)
+			midToSlope[mid] = append(midToSlope[mid], k)
+		}
+	}
+
+	for _, sti := range slopeToIntercept {
+		if len(sti) == 1 {
+			continue
+		}
+
+		cnt := make(map[float64]int)
+		for _, bVal := range sti {
+			cnt[bVal]++
+		}
+
+		totalSum := 0
+		for _, count := range cnt {
+			ans += totalSum * count
+			totalSum += count
+		}
+	}
+
+	for _, mts := range midToSlope {
+		if len(mts) == 1 {
+			continue
+		}
+
+		cnt := make(map[float64]int)
+		for _, kVal := range mts {
+			cnt[kVal]++
+		}
+
+		totalSum := 0
+		for _, count := range cnt {
+			ans -= totalSum * count
+			totalSum += count
+		}
+	}
+
+	return ans
 }

leetcode/3601-3700/3625.Count-Number-of-Trapezoids-II/Solution_test.go

@@ -10,12 +10,11 @@ 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{{-3, 2}, {3, 0}, {2, 3}, {3, 2}, {2, -3}}, 2},
+		{"TestCase2", [][]int{{0, 0}, {1, 0}, {0, 1}, {2, 1}}, 1},
 	}
 
 	//	开始测试
@@ -30,10 +29,10 @@ 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() {
 }