From 0dbb8d49e919e1f2f2cff83eb17a6ac3eed00ce8 Mon Sep 17 00:00:00 2001
From: Matej Focko <me@mfocko.xyz>
Date: Sun, 18 Aug 2024 12:23:00 +0200
Subject: [PATCH] =?UTF-8?q?go:=20add=20=C2=AB264.=20Ugly=20Number=20II?=
 =?UTF-8?q?=C2=BB?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Matej Focko <me@mfocko.xyz>
---
 go/ugly-number-ii.go | 50 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 go/ugly-number-ii.go

diff --git a/go/ugly-number-ii.go b/go/ugly-number-ii.go
new file mode 100644
index 0000000..34bd08e
--- /dev/null
+++ b/go/ugly-number-ii.go
@@ -0,0 +1,50 @@
+package main
+
+import (
+	"cmp"
+	"slices"
+)
+
+type Factor struct {
+	factor int
+	index  int
+	next   int
+}
+
+func MakeFactor(factor int) Factor {
+	return Factor{
+		factor: factor,
+		index:  0,
+		next:   factor,
+	}
+}
+
+func (f *Factor) Update(ugly []int, last int) {
+	if last != f.next {
+		return
+	}
+
+	f.index++
+	f.next = f.factor * ugly[f.index]
+}
+
+func nthUglyNumber(n int) int {
+	ugly := make([]int, n)
+	ugly[0] = 1
+
+	factors := []Factor{
+		MakeFactor(2), MakeFactor(3), MakeFactor(5),
+	}
+
+	for i := 1; i < n; i++ {
+		ugly[i] = slices.MinFunc(factors, func(a, b Factor) int {
+			return cmp.Compare(a.next, b.next)
+		}).next
+
+		for j, _ := range factors {
+			factors[j].Update(ugly, ugly[i])
+		}
+	}
+
+	return ugly[n-1]
+}