From d4a3d8f89bef07d04e953efb838366649119fe96 Mon Sep 17 00:00:00 2001
From: Luke Hubmayer-Werner <mongoose41@gmail.com>
Date: Tue, 6 Dec 2022 23:34:01 +1030
Subject: [PATCH] Nim losing to Scala (again)

---
 2022/day6.scala | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/2022/day6.scala b/2022/day6.scala
index 8ee3629..367d624 100644
--- a/2022/day6.scala
+++ b/2022/day6.scala
@@ -2,7 +2,7 @@ import java.nio.file.Files
 import java.nio.file.Paths
 import scala.util.control.NonLocalReturns.*
 
-// scala day6.jar  52.22s user 0.54s system 100% cpu 52.389 total
+// 1M iterations: scala day6.jar  52.22s user 0.54s system 100% cpu 52.389 total
 extension (s: String) def noDuplicates: Boolean =
 	var i = 0
 	while i < (s.length-1) do
@@ -21,12 +21,24 @@ def first_unique_run_for(line: String, num: Int, skip: Int = 0): Int = returning
 	throwReturn(-1)
 }
 
-def first_unique_run_while(line: String, num: Int, skip: Int = 0): Int =
-	var i = num.max(skip)
-	while i < line.length do
-		if line.substring(i-num, i).toCharArray.distinct.size == num then
-			return i
+// 1M iterations: scala day6.jar  20.44s user 0.07s system 100% cpu 20.371 total
+def no_duplicates_copyless(s: String, right: Int, length: Int): Boolean =
+	var i = right - length + 1
+	while i < right do
+		val c = s(i)
+		var j = i + 1
+		while j <= right do
+			if c == s(j) then return false
+			j += 1
 		i += 1
+	return true
+
+def first_unique_run_while(line: String, num: Int, skip: Int = 0): Int =
+	var right = num.max(skip)
+	while right < line.length do
+		if no_duplicates_copyless(line, right, num) then
+			return right
+		right += 1
 	return -1
 
 @main def main() =
@@ -44,7 +56,7 @@ def perf_test(line: String, n: Int) =
 	var four = -1
 	var fourteen = -1
 	for i <- 1 to n do
-		four = first_unique_run_for(line, 4)
-		fourteen = first_unique_run_for(line, 14, four)
+		four = first_unique_run_while(line, 4)
+		fourteen = first_unique_run_while(line, 14, four)
 	println(four)
 	println(fourteen)