day 8 tidy up and optimisations

scottmckendry · Dec 8, 2024 · b384926 · b384926
1 parent c88b8ec
commit b384926
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Showing 3 changed files with 41 additions and 93 deletions.
diff --git a/2024/08p1.odin b/2024/08p1.odin
@@ -18,7 +18,7 @@ D08P1 :: proc() {
 
 get_antinode_count :: proc(lines: []string) -> int {
     antennas := parse_antennas(lines)
-    antinodes := [dynamic]vec2{}
+    antinodes := make(map[vec2]bool)
     defer {
         for _, antennas_at_frequency in antennas {
             delete(antennas_at_frequency)
@@ -34,7 +34,7 @@ get_antinode_count :: proc(lines: []string) -> int {
     for _, antennas_at_frequency in antennas {
         for antenna1, i in antennas_at_frequency {
             for antenna2, j in antennas_at_frequency {
-                if i == j {
+                if i >= j { // skip duplicate pairs
                     continue
                 }
 
@@ -55,18 +55,17 @@ get_antinode_count :: proc(lines: []string) -> int {
     return len(antinodes)
 }
 
-check_antinode :: proc(antinodes: ^[dynamic]vec2, antinode: vec2, max_x: int, max_y: int) -> bool {
+check_antinode :: proc(antinodes: ^map[vec2]bool, antinode: vec2, max_x: int, max_y: int) -> bool {
     if antinode.x < 0 || antinode.x >= max_x || antinode.y < 0 || antinode.y >= max_y {
         return false
     }
 
-    for existing in antinodes^ {
-        if existing.x == antinode.x && existing.y == antinode.y {
-            return true
-        }
+    _, found := antinodes^[antinode]
+    if found {
+        return true
     }
 
-    append(antinodes, antinode)
+    antinodes[antinode] = true
 
     return true
 }

diff --git a/2024/08p2.odin b/2024/08p2.odin
@@ -13,7 +13,7 @@ D08P2 :: proc() {
 
 get_antinode_count_p2 :: proc(lines: []string) -> int {
 	antennas := parse_antennas(lines)
-	antinodes := [dynamic]vec2{}
+	antinodes := make(map[vec2]bool)
 	defer {
 		for _, antennas_at_frequency in antennas {
 			delete(antennas_at_frequency)
@@ -29,7 +29,7 @@ get_antinode_count_p2 :: proc(lines: []string) -> int {
 	for _, antennas_at_frequency in antennas {
 		for antenna1, i in antennas_at_frequency {
 			for antenna2, j in antennas_at_frequency {
-				if i == j {
+				if i >= j { 	// skip duplicate pairs
 					continue
 				}
 
@@ -39,53 +39,30 @@ get_antinode_count_p2 :: proc(lines: []string) -> int {
 					antenna2.position.y - antenna1.position.y,
 				}
 
-				// simplify the vector (if possible) e.g. (1, 2) -> (1, 2), (2, 4) -> (1, 2)
-				vec = simplify_vector(vec)
-
-				// first check all valid antinodes by adding the vector to the first antenna
-				in_bounds := true
-				pos := vec2{antenna1.position.x + vec.x, antenna1.position.y + vec.y}
-				for in_bounds {
-					in_bounds = check_antinode(&antinodes, pos, max_x, max_y)
-					pos.x += vec.x
-					pos.y += vec.y
-				}
-
-				// then check all valid antinodes by subtracting the vector from the second antenna 
-				// this ensures that any nodes inbetween the two antennas are counted
-				in_bounds = true
-				pos = vec2{antenna2.position.x, antenna2.position.y}
-				for in_bounds {
-					in_bounds = check_antinode(&antinodes, pos, max_x, max_y)
-					pos.x -= vec.x
-					pos.y -= vec.y
-				}
+				check_antinode_direction(antenna1.position, vec, &antinodes, max_x, max_y)
+				check_antinode_direction(
+					antenna2.position,
+					vec2{-vec.x, -vec.y},
+					&antinodes,
+					max_x,
+					max_y,
+				)
 			}
 		}
 	}
 
 	return len(antinodes)
 }
 
-simplify_vector :: proc(vec: vec2) -> vec2 {
-	vec_copy := vec
-	// find the greatest common divisor of the vector components
-	gcd := find_gcd(vec.x, vec.y)
-
-	// simplify the vector
-	vec_copy.x /= gcd
-	vec_copy.y /= gcd
-
-	return vec
-}
-
-find_gcd :: proc(a, b: int) -> int {
-	a_copy := a
-	b_copy := b
-
-	for b_copy != 0 {
-		a_copy, b_copy = b_copy, a_copy % b_copy
+check_antinode_direction :: proc(
+	start: vec2,
+	vec: vec2,
+	antinodes: ^map[vec2]bool,
+	max_x, max_y: int,
+) {
+	pos := start
+	for check_antinode(antinodes, pos, max_x, max_y) {
+		pos.x += vec.x
+		pos.y += vec.y
 	}
-
-	return a
 }
diff --git a/2024/tests/08_test.odin b/2024/tests/08_test.odin
@@ -2,23 +2,23 @@ package main
 
 import "core:fmt"
 import "core:testing"
+antenna_map :: []string {
+	"............",
+	"........0...",
+	".....0......",
+	".......0....",
+	"....0.......",
+	"......A.....",
+	"............",
+	"............",
+	"........A...",
+	".........A..",
+	"............",
+	"............",
+}
 
 @(test)
 d08p1 :: proc(t: ^testing.T) {
-	antenna_map := []string {
-		"............",
-		"........0...",
-		".....0......",
-		".......0....",
-		"....0.......",
-		"......A.....",
-		"............",
-		"............",
-		"........A...",
-		".........A..",
-		"............",
-		"............",
-	}
 	want := 14
 	got := get_antinode_count(antenna_map)
 	testing.expect(t, got == want, fmt.aprintf("Got: %v | Want: %v", got, want))
@@ -28,20 +28,6 @@ d08p1 :: proc(t: ^testing.T) {
 
 @(test)
 d08p2 :: proc(t: ^testing.T) {
-	antenna_map := []string {
-		"............",
-		"........0...",
-		".....0......",
-		".......0....",
-		"....0.......",
-		"......A.....",
-		"............",
-		"............",
-		"........A...",
-		".........A..",
-		"............",
-		"............",
-	}
 	want := 34
 	got := get_antinode_count_p2(antenna_map)
 	testing.expect(t, got == want, fmt.aprintf("Got: %v | Want: %v", got, want))
@@ -51,20 +37,6 @@ d08p2 :: proc(t: ^testing.T) {
 
 @(test)
 test_parse_antennas :: proc(t: ^testing.T) {
-	antenna_map := []string {
-		"............",
-		"........0...",
-		".....0......",
-		".......0....",
-		"....0.......",
-		"......A.....",
-		"............",
-		"............",
-		"........A...",
-		".........A..",
-		"............",
-		"............",
-	}
 	got := parse_antennas(antenna_map)
 	want_A0 := antenna{vec2{6, 5}, 'A'}
 	want_03 := antenna{vec2{4, 4}, '0'}