1 files changed, 152 insertions, 0 deletions
diff --git a/challenge-148/pokgopun/go/ch-2.go b/challenge-148/pokgopun/go/ch-2.go
new file mode 100644
index 0000000000..5c3c3bb22d
--- /dev/null
+++ b/challenge-148/pokgopun/go/ch-2.go
@@ -0,0 +1,152 @@
+// From https://math.stackexchange.com/questions/1885095/parametrization-of-cardano-triplet
+// a = 3k + 2
+// b^2 * c = (k+1)^2 * (8k + 5)
+package main
+
+import (
+	"fmt"
+	"math"
+	"sort"
+	"strings"
+)
+
+func main() {
+	cdn := newCdn3(400)
+	fmt.Println(cdn)
+}
+
+func pmap(n uint) []bool {
+	m := make([]bool, int(n)+1)
+	for i := 2; i <= int(n); i++ {
+		m[i] = true
+	}
+	for i := 2; float64(i) <= math.Sqrt(float64(n)); i++ {
+		j := i * i
+		for j <= int(n) {
+			m[j] = false
+			j += i
+		}
+
+	}
+	return m
+}
+
+type cdn3 struct {
+	k     uint
+	pmap  []bool
+	plist []int
+}
+
+func newCdn3(n uint) (c cdn3) {
+	c.k = n
+	// create prime map as large as sqrt of (8k + 5) which is the term we need to do factoriing
+	//c.pmap = pmap(uint(math.Floor(math.Sqrt(float64(8*n) + 5))))
+	// create prime map as large as (8k + 5) to make it easy to check prime for factoring the number
+	c.pmap = pmap(uint((8 * n) + 5))
+	for i := 2; i < len(c.pmap); i++ {
+		if c.pmap[i] {
+			c.plist = append(c.plist, i)
+		}
+	}
+	return c
+}
+
+func (cdn cdn3) a(k uint) int {
+	return int(3*k + 2)
+}
+
+func (cdn cdn3) bc(k uint) (s [][2]int) {
+	b := int(k + 1)
+	c := int(8*k + 5)
+	//bIsPrime := big.NewInt(int64(b)).ProbablyPrime(10)
+	//cIsPrime := big.NewInt(int64(c)).ProbablyPrime(10)
+	s = append(s, [2]int{1, b * b * c})
+	factor := []int{}
+	if cdn.pmap[c] {
+		if b == 1 {
+			return s
+		}
+		if cdn.pmap[b] {
+			s = append(s, [2]int{b, c})
+			return s
+		} else {
+			factor = append(factor, cdn.factor(b)...)
+			factor = append(factor, factor...)
+			factor = append(factor, c)
+		}
+	} else {
+		if cdn.pmap[b] {
+			factor = append(factor, b, b)
+		} else {
+			factor = append(factor, cdn.factor(b)...)
+			factor = append(factor, factor...)
+		}
+		factor = append(factor, cdn.factor(c)...)
+	}
+	sort.SliceStable(factor, func(i, j int) bool {
+		return factor[i] < factor[j]
+	})
+	fmt.Println("b =", b, "c =", c, "factor =>", factor, len(factor))
+	var (
+		prev       int
+		pair, lone []int
+	)
+	for _, v := range factor {
+		if prev == v {
+			pair = append(pair, v)
+			prev = 0
+		} else if prev == 0 {
+			prev = v
+		} else {
+			lone = append(lone, prev)
+			prev = v
+		}
+	}
+	if prev != 0 {
+		lone = append(lone, prev)
+	}
+	fmt.Println("factor =>", "pair =", pair, "lone =", lone)
+	return s
+}
+
+func (cdn cdn3) factor(n int) (s []int) {
+	if n > 1 {
+		if cdn.pmap[n] {
+			return []int{n}
+		}
+		i := 0
+		for {
+			if n%cdn.plist[i] != 0 {
+				i++
+			} else {
+				s = append(s, cdn.plist[i])
+				n /= cdn.plist[i]
+				if n == 1 {
+					break
+				} else if cdn.pmap[n] {
+					s = append(s, n)
+					break
+				}
+			}
+		}
+	}
+	return s
+}
+
+func (cdn cdn3) abc(k uint) (s [][3]int) {
+	for _, v := range cdn.bc(k) {
+		s = append(s, [3]int{cdn.a(k), v[0], v[1]})
+	}
+	return s
+}
+
+func (cdn cdn3) String() string {
+	var b strings.Builder
+	for k := 0; k <= int(cdn.k); k++ {
+		for _, v := range cdn.abc(uint(k)) {
+			//fmt.Println(v)
+			b.WriteString(fmt.Sprintln(v))
+		}
+	}
+	return b.String()
+}