Add solution and test-cases for problem 812

leetcode/801-900/0812.Largest-Triangle-Area/README.md

@@ -1,28 +1,24 @@
 # [812.Largest Triangle Area][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
+Given an array of points on the **X-Y** plane `points` where `points[i] = [xi, yi]`, return the area of the largest triangle that can be formed by any three different points. Answers within 10-5 of the actual answer will be accepted.
+
+**Example 1:**  
 
-**Example 1:**
+![1](./1.png)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: points = [[0,0],[0,1],[1,0],[0,2],[2,0]]
+Output: 2.00000
+Explanation: The five points are shown in the above figure. The red triangle is the largest.
 ```
 
-## 题意
-> ...
-
-## 题解
+**Example 2:**
 
-### 思路1
-> ...
-Largest Triangle Area
-```go
 ```
-
+Input: points = [[1,0],[0,0],[0,1]]
+Output: 0.50000
+```
 
 ## 结语
 

leetcode/801-900/0812.Largest-Triangle-Area/Solution.go

@@ -1,5 +1,33 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+import "math"
+
+const epsilon = 1e-9
+
+func canForm(a, b, c []int) (float64, bool) {
+	abx := b[0] - a[0]
+	aby := b[1] - a[1]
+	acx := c[0] - a[0]
+	acy := c[1] - a[1]
+	area := math.Abs(float64(abx*acy - aby*acx))
+	if area > epsilon {
+		return area, true
+	}
+	return 0.0, false
+}
+
+func Solution(points [][]int) float64 {
+	var ret float64
+	l := len(points)
+	for i := 0; i < l-2; i++ {
+		for j := i + 1; j < l-1; j++ {
+			for k := j + 1; k < l; k++ {
+				area, ok := canForm(points[i], points[j], points[k])
+				if ok {
+					ret = max(ret, area/2.0)
+				}
+			}
+		}
+	}
+	return ret
 }

leetcode/801-900/0812.Largest-Triangle-Area/Solution_test.go

@@ -10,12 +10,14 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs [][]int
+		expect float64
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", [][]int{
+			{0, 0}, {0, 1}, {1, 0}, {0, 2}, {2, 0}}, 2.00000},
+		{"TestCase", [][]int{
+			{1, 0}, {0, 0}, {0, 1},
+		}, 0.50000},
 	}
 
 	//	开始测试
@@ -30,10 +32,10 @@ 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() {
 }