添加 18 题

leetcode/0812.Largest-Triangle-Area/812. Largest Triangle Area.go

@@ -0,0 +1,31 @@
+package leetcode
+
+func largestTriangleArea(points [][]int) float64 {
+	maxArea, n := 0.0, len(points)
+	for i := 0; i < n; i++ {
+		for j := i + 1; j < n; j++ {
+			for k := j + 1; k < n; k++ {
+				maxArea = max(maxArea, area(points[i], points[j], points[k]))
+			}
+		}
+	}
+	return maxArea
+}
+
+func area(p1, p2, p3 []int) float64 {
+	return abs(p1[0]*p2[1]+p2[0]*p3[1]+p3[0]*p1[1]-p1[0]*p3[1]-p2[0]*p1[1]-p3[0]*p2[1]) / 2
+}
+
+func abs(num int) float64 {
+	if num < 0 {
+		num = -num
+	}
+	return float64(num)
+}
+
+func max(a, b float64) float64 {
+	if a > b {
+		return a
+	}
+	return b
+}

leetcode/0812.Largest-Triangle-Area/812. Largest Triangle Area_test.go

@@ -0,0 +1,42 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question812 struct {
+	para812
+	ans812
+}
+
+// para 是参数
+// one 代表第一个参数
+type para812 struct {
+	one [][]int
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans812 struct {
+	one float64
+}
+
+func Test_Problem812(t *testing.T) {
+
+	qs := []question812{
+
+		question812{
+			para812{[][]int{[]int{0, 0}, []int{0, 1}, []int{1, 0}, []int{0, 2}, []int{2, 0}}},
+			ans812{2.0},
+		},
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 812------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans812, q.para812
+		fmt.Printf("【input】:%v       【output】:%v\n", p, largestTriangleArea(p.one))
+	}
+	fmt.Printf("\n\n\n")
+}

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

@@ -0,0 +1,70 @@
+# [812. Largest Triangle Area](https://leetcode.com/problems/largest-triangle-area/)
+
+
+## 题目
+
+You have a list of points in the plane. Return the area of the largest triangle that can be formed by any 3 of the points.
+
+```
+Example:
+Input: points = [[0,0],[0,1],[1,0],[0,2],[2,0]]
+Output: 2
+Explanation: 
+The five points are show in the figure below. The red triangle is the largest.
+```
+
+![https://s3-lc-upload.s3.amazonaws.com/uploads/2018/04/04/1027.png](https://s3-lc-upload.s3.amazonaws.com/uploads/2018/04/04/1027.png)
+
+**Notes**:
+
+- `3 <= points.length <= 50`.
+- No points will be duplicated.
+- `-50 <= points[i][j] <= 50`.
+- Answers within `10^-6` of the true value will be accepted as correct.
+
+## 题目大意
+
+给定包含多个点的集合，从其中取三个点组成三角形，返回能组成的最大三角形的面积。
+
+## 解题思路
+
+- 给出一组点的坐标，要求找出能组成三角形面积最大的点集合，输出这个最大面积。
+- 数学题。按照数学定义，分别计算这些能构成三角形的点形成的三角形面积，最终输出最大面积即可。
+
+## 代码
+
+```go
+
+package leetcode
+
+func largestTriangleArea(points [][]int) float64 {
+	maxArea, n := 0.0, len(points)
+	for i := 0; i < n; i++ {
+		for j := i + 1; j < n; j++ {
+			for k := j + 1; k < n; k++ {
+				maxArea = max(maxArea, area(points[i], points[j], points[k]))
+			}
+		}
+	}
+	return maxArea
+}
+
+func area(p1, p2, p3 []int) float64 {
+	return abs(p1[0]*p2[1]+p2[0]*p3[1]+p3[0]*p1[1]-p1[0]*p3[1]-p2[0]*p1[1]-p3[0]*p2[1]) / 2
+}
+
+func abs(num int) float64 {
+	if num < 0 {
+		num = -num
+	}
+	return float64(num)
+}
+
+func max(a, b float64) float64 {
+	if a > b {
+		return a
+	}
+	return b
+}
+
+```