From 2d9dc1b236e84c65d51c66b765f049c4183fa50b Mon Sep 17 00:00:00 2001
From: Elias Kohout <elias@kohout.de>
Date: Sat, 7 Dec 2024 00:47:35 +0100
Subject: [PATCH] performance improvement on part 2 of day 6, but still not a
 correct result

---
 day6/data.txt      |  1 -
 day6/loop_guard.go | 50 ++++++++++++++++------------------------------
 2 files changed, 17 insertions(+), 34 deletions(-)

diff --git a/day6/data.txt b/day6/data.txt
index 6aa3008..7ae77b7 100644
--- a/day6/data.txt
+++ b/day6/data.txt
@@ -128,4 +128,3 @@
 ...........................#..............#.....#............#.....................#........#....#.......................#........
 ........#..##................#.....#.#..............#..............................#........................#.........#...........
 .........................................................#...........................##..........#........#.##....................
-
diff --git a/day6/loop_guard.go b/day6/loop_guard.go
index 8da1f3e..9133916 100644
--- a/day6/loop_guard.go
+++ b/day6/loop_guard.go
@@ -5,7 +5,10 @@ import (
     "fmt"
     "strings"
 )
+
+
 // type definitions
+
 type Direction int
 const (
 	Up Direction = iota + 1
@@ -26,8 +29,8 @@ func new_state(text string) *state {
     field := make([][]rune, len(lines))
     guard := [2]int{-1,-1}
 
-    for y := range lines {
-        field[y] = []rune(lines[y])
+    for y, line := range lines {
+        field[y] = []rune(line)
 
         for x, r := range field[y] {
             if r == '^' {
@@ -41,24 +44,16 @@ func new_state(text string) *state {
     return &s
 }
 
-func (s *state) equals(other *state) bool {
-    return s.guard_x == other.guard_x && s.guard_y == other.guard_y && s.direction == other.direction
-}
 
 // general util
+
 func check(e error) {
     if e != nil { panic(e) }
 }
 
-func add_non_duplicate(slice []*state, elem *state) []*state {
-    for _, e := range slice {
-        if e.equals(elem) { return slice }
-    }
-    return append(slice, elem)
-}
-
 
 // simulation functions
+
 func iter(s *state) *state {
     new_guard_x := s.guard_x
     new_guard_y := s.guard_y
@@ -109,35 +104,24 @@ func iter(s *state) *state {
 }
 
 func will_loop(s *state) bool {
-    distinct_states := make([]*state, 0, 130 * 130 * 4)
+    counter := 0
     // while guard is within the field
-    for s.guard_x >= 0 {
-        // store copy of the current state
-        old_len := len(distinct_states)
-        cpy := state{
-            field: s.field,
-            guard_x: s.guard_x,
-            guard_y: s.guard_y,
-            direction: s.direction,
-        }
-        distinct_states = add_non_duplicate(distinct_states, &cpy)
-
-        // if duplicate state found, loop found
-        if len(distinct_states) == old_len {
-            return true
-        }
-
+    for s.guard_x >= 0 && counter < 10000 {
         // iterate
         s = iter(s)
+        counter++
+    }
+    if s.guard_x < 0 {
+        // the guard is no longer in the field, not a loop
+        return false
+    } else {
+        return true
     }
-    // the guard is no longer in the field, not a loop
-    return false
 }
 
-
 func print(s *state) {
     out := make([]string, 0, len(*s.field))
-    for _, line := range *s.field {
+    for line := range *s.field {
         out = append(out, string(line))
     }
     fmt.Println(strings.Join(out, "\n"))