20210112

20210109/main.go

@@ -4,15 +4,15 @@ func main() {
 
 }
 
-func search(n int, nums []int) int {
+func search(target int, nums []int) int {
 	low, high := 0, len(nums)-1
 	for low <= high {
 		mid := low + (high-low)/2
-		if nums[mid] == n {
+		if nums[mid] == target {
 			return mid
-		} else if n < nums[mid] {
+		} else if target < nums[mid] {
 			high = mid - 1
-		} else if n > nums[mid] {
+		} else if target > nums[mid] {
 			low = mid + 1
 		}
 	}

58_spiral_primes/main.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+)
+
+func main() {
+	n := 26239
+	for {
+		fmt.Println(n)
+		nums, err := findSprialDiagonals(n)
+		if err != nil {
+			fmt.Println(err)
+			break
+		}
+		if primeRatio(nums) < 0.1 {
+			fmt.Println(n)
+			break
+		}
+		n += 2
+	}
+}
+
+func findSprialDiagonals(width int) ([]int, error) {
+	if width%2 == 0 {
+		return nil, errors.New("invalid width")
+	}
+	x := 3
+	ret := []int{1}
+	cw := 3
+	d := 2
+	for width/cw > 0 {
+		ret = append(ret, []int{x, x + d, x + 2*d, x + 3*d}...)
+		x = x + 3*d + cw + 1
+		cw += 2
+		d = cw - 1
+	}
+	return ret, nil
+}
+
+func primeRatio(nums []int) float64 {
+	pc := float64(0)
+	for _, n := range nums {
+		if isPrime(n) {
+			pc++
+		}
+	}
+	return pc / float64(len(nums))
+}
+
+func isPrime(n int) bool {
+	if n <= 1 {
+		return false
+	}
+	res := n
+	//牛顿法求平方根
+	for res*res > n {
+		res = (res + n/res) / 2
+	}
+	divider := 2
+	for divider <= res {
+		if n%divider == 0 {
+			return false
+		}
+		divider++
+	}
+	return true
+}

58_spiral_primes/main_test.go

@@ -0,0 +1,27 @@
+package main
+
+import "testing"
+
+func Test_primeRatio(t *testing.T) {
+	type args struct {
+		nums []int
+	}
+	tests := []struct {
+		name string
+		args args
+		want float64
+	}{
+		{
+			"test1",
+			args{[]int{2, 3, 5, 8}},
+			0.75,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := primeRatio(tt.args.nums); got != tt.want {
+				t.Errorf("primeRatio() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}