478 wrong answer

Author: aQua

.vscode/bookmarks.json

@@ -8,5 +8,15 @@
 				"label": ""
 			}
 		]
+	},
+	{
+		"path": "$ROOTPATH$/Algorithms/0478.generate-random-point-in-a-circle/generate-random-point-in-a-circle.go",
+		"bookmarks": [
+			{
+				"line": 29,
+				"column": 11,
+				"label": ""
+			}
+		]
 	}
 ]

Algorithms/0478.generate-random-point-in-a-circle/README.md

@@ -0,0 +1,38 @@
+# [478. Generate Random Point in a Circle](https://leetcode.com/problems/generate-random-point-in-a-circle/)
+
+## 题目
+
+Given the radius and x-y positions of the center of a circle, write a function `randPoint` which generates a uniform randompoint in the circle.
+
+Note:
+
+1. input and output values are in [floating-point](https://www.webopedia.com/TERM/F/floating_point_number.html).
+1. radius and x-y position of the center of the circle is passed into the class constructor.
+1. a point on the circumference of the circle is considered to bein the circle.
+1. randPointreturnsa size 2 array containing x-position and y-position of the random point, in that order.
+
+Example 1:
+
+```text
+Input:
+["Solution","randPoint","randPoint","randPoint"]
+[[1,0,0],[],[],[]]
+Output: [null,[-0.72939,-0.65505],[-0.78502,-0.28626],[-0.83119,-0.19803]]
+```
+
+Example 2:
+
+```text
+Input:
+["Solution","randPoint","randPoint","randPoint"]
+[[10,5,-7.5],[],[],[]]
+Output: [null,[11.52438,-8.33273],[2.46992,-16.21705],[11.13430,-12.42337]]
+```
+
+Explanation of Input Syntax:
+
+The input is two lists:the subroutines calledand theirarguments.Solution'sconstructor has three arguments, the radius, x-position of the center, and y-position of the center of the circle. randPoint has no arguments.Argumentsarealways wrapped with a list, even if there aren't any.
+
+## 解题思路
+
+见程序注释

Algorithms/0478.generate-random-point-in-a-circle/generate-random-point-in-a-circle.go

@@ -0,0 +1,36 @@
+package problem0478
+
+import (
+	"math"
+	"math/rand"
+)
+
+// Solution object will be instantiated and called as such:
+// obj := Constructor(radius, x_center, y_center);
+// param_1 := obj.RandPoint();
+type Solution struct {
+	r, a, b, ratio float64
+}
+
+// Constructor 构建 Solution
+func Constructor(radius, xCenter, yCenter float64) Solution {
+	ratio := 1.
+	if radius < 1 {
+		radius = 1.
+		ratio = 1. / radius
+	}
+	return Solution{
+		r:     radius,
+		a:     xCenter,
+		b:     yCenter,
+		ratio: ratio,
+	}
+}
+
+// RandPoint 返回随机点
+func (s *Solution) RandPoint() []float64 {
+	rjd := rand.Float64()
+	x := s.a + s.r*math.Sin(rjd)
+	y := s.b + s.r*math.Cos(rjd)
+	return []float64{x / s.ratio, y / s.ratio}
+}

Algorithms/0478.generate-random-point-in-a-circle/generate-random-point-in-a-circle_test.go

@@ -0,0 +1,32 @@
+package problem0478
+
+import (
+	"math"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_RandPoint(t *testing.T) {
+	ast := assert.New(t)
+	r, a, b := 3., 2., 1.
+	s := Constructor(r, a, b)
+	for i := 0; i < 100; i++ {
+		p := s.RandPoint()
+		x, y := p[0], p[1]
+		actual := math.Sqrt((x-a)*(x-a) + (y-b)*(y-b))
+		ast.InDelta(r, actual, 0.00001)
+	}
+}
+
+func Test_RandPoint_2(t *testing.T) {
+	ast := assert.New(t)
+	r, a, b := 0.01, -73839.1, -3289891.
+	s := Constructor(r, a, b)
+	for i := 0; i < 100; i++ {
+		p := s.RandPoint()
+		x, y := p[0], p[1]
+		actual := math.Sqrt((x-a)*(x-a) + (y-b)*(y-b))
+		ast.InDelta(r, actual, 0.00001)
+	}
+}