From 17e5d18ffc77c16998b9183dd1073000c0f866a8 Mon Sep 17 00:00:00 2001
From: Scott McKendry <39483124+scottmckendry@users.noreply.github.com>
Date: Mon, 9 Dec 2024 09:18:29 +1300
Subject: [PATCH] improve day 6 pt 2 execution time

---
 2024/06p1.odin          | 15 +++++++++----
 2024/06p2.odin          | 47 ++++++++++++++++++-----------------------
 2024/tests/06_test.odin |  2 +-
 3 files changed, 33 insertions(+), 31 deletions(-)

diff --git a/2024/06p1.odin b/2024/06p1.odin
index 8e77c25..80a2a0a 100644
--- a/2024/06p1.odin
+++ b/2024/06p1.odin
@@ -16,17 +16,23 @@ D06P1 :: proc() {
 	input_string := #load("inputs/06.txt", string)
 	lines := strings.split(input_string, "\n", context.temp_allocator)
 
-	unique_guard_positions := get_unique_guard_positions(lines[:len(lines) - 1])
+	unique_guard_positions, throw_away := get_unique_guard_positions(lines[:len(lines) - 1])
+	delete(throw_away)
 	fmt.printf("Unique guard positions: %d\n", unique_guard_positions)
 }
 
-get_unique_guard_positions :: proc(lines: []string) -> int {
+get_unique_guard_positions :: proc(
+	lines: []string,
+) -> (
+	visited_count: int,
+	unique_positions: [dynamic]vec2,
+) {
 	lab_map, guard_position, max_x, max_y := parse_lab_map(lines)
 	defer delete(lab_map)
 
 	guard_direction := vec2{0, -1}
 
-	visited_count := 1
+	visited_count = 1
 
 	on_map := true
 	for on_map {
@@ -50,6 +56,7 @@ get_unique_guard_positions :: proc(lines: []string) -> int {
 			guard_position = next_position
 			if !lab_map[guard_position].visited {
 				visited_count += 1
+				append(&unique_positions, guard_position)
 				guard_map_coord := lab_map[guard_position]
 				guard_map_coord.visited = true
 				lab_map[guard_position] = guard_map_coord
@@ -72,7 +79,7 @@ get_unique_guard_positions :: proc(lines: []string) -> int {
 		}
 	}
 
-	return visited_count
+	return
 }
 
 parse_lab_map :: proc(
diff --git a/2024/06p2.odin b/2024/06p2.odin
index 105ebf0..824b817 100644
--- a/2024/06p2.odin
+++ b/2024/06p2.odin
@@ -3,7 +3,7 @@ package main
 import "core:fmt"
 import "core:strings"
 
-type_visited :: struct {
+position_state :: struct {
 	position, direction: vec2,
 }
 
@@ -17,33 +17,32 @@ D06P2 :: proc() {
 
 get_loop_causing_obstacles :: proc(lines: []string) -> int {
 	original_map, guard_position, max_x, max_y := parse_lab_map(lines)
+	_, positions_to_check := get_unique_guard_positions(lines)
 	defer delete(original_map)
+	defer delete(positions_to_check)
 
 	loop_count := 0
 
 	// place a obstable at each possible position, and check if it causes a loop
-	for y in 0 ..< max_y {
-		for x in 0 ..< max_x {
-			if original_map[vec2{x, y}].is_obstacle ||
-			   (x == guard_position.x && y == guard_position.y) {
-				continue
-			}
+	for position in positions_to_check {
+		if (position.x == guard_position.x && position.y == guard_position.y) {
+			continue
+		}
 
-			// create a new map and copy all entries
-			lab_map := make(map[vec2]lab_map_coord)
-			for k, v in original_map {
-				lab_map[k] = v
-			}
-			defer delete(lab_map)
+		// create a new map and copy all entries
+		lab_map := make(map[vec2]lab_map_coord)
+		for k, v in original_map {
+			lab_map[k] = v
+		}
+		defer delete(lab_map)
 
-			// update the new position
-			coord_to_update := lab_map[vec2{x, y}]
-			coord_to_update.is_obstacle = true
-			lab_map[vec2{x, y}] = coord_to_update
+		// update the new position
+		coord_to_update := lab_map[position]
+		coord_to_update.is_obstacle = true
+		lab_map[position] = coord_to_update
 
-			if check_for_loop(lab_map, guard_position, max_x, max_y) {
-				loop_count += 1
-			}
+		if check_for_loop(lab_map, guard_position, max_x, max_y) {
+			loop_count += 1
 		}
 	}
 
@@ -58,17 +57,13 @@ check_for_loop :: proc(
 	guard_direction := vec2{0, -1}
 	guard_pos := guard_position
 
-	Position_State :: struct {
-		pos: vec2,
-		dir: vec2,
-	}
-	visited_states := make(map[Position_State]bool)
+	visited_states := make(map[position_state]bool)
 	defer delete(visited_states)
 
 	on_map := true
 
 	for on_map {
-		current_state := Position_State{guard_pos, guard_direction}
+		current_state := position_state{guard_pos, guard_direction}
 		if visited_states[current_state] {
 			return true
 		}
diff --git a/2024/tests/06_test.odin b/2024/tests/06_test.odin
index f04d5b4..b5a3971 100644
--- a/2024/tests/06_test.odin
+++ b/2024/tests/06_test.odin
@@ -18,7 +18,7 @@ d06p1 :: proc(t: ^testing.T) {
 		"......#...",
 	}
 	want := 41
-	got := get_unique_guard_positions(lab_map)
+	got, _ := get_unique_guard_positions(lab_map)
 	testing.expect(t, got == want, fmt.aprintf("Got: %v | Want: %v", got, want))
 
 	free_all()