commit 328fcd1c0ebf48d91ea2323e9a35017cb15d28e8
parent c80ff36745187674bd373354d3f41b2d3548a866
Author: Shimmy Xu <shimmy.xu@shimmy1996.com>
Date: Sat, 12 Dec 2020 07:05:21 -0600
Add 2020 day 12
Diffstat:
| A | 2020/day12/input.txt | | | 773 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| A | 2020/day12/main.go | | | 121 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
2 files changed, 894 insertions(+), 0 deletions(-)
diff --git a/2020/day12/input.txt b/2020/day12/input.txt
@@ -0,0 +1,773 @@
+R180
+S1
+F44
+R90
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diff --git a/2020/day12/main.go b/2020/day12/main.go
@@ -0,0 +1,121 @@
+package main
+
+import (
+ "bufio"
+ "fmt"
+ "os"
+ "strconv"
+)
+
+const (
+ N = iota
+ S
+ E
+ W
+ L
+ R
+ F
+)
+
+type navi struct {
+ len int
+ act []int
+ val []int
+}
+
+func (this *navi) get(i int) (int, int) {
+ return this.act[i], this.val[i]
+}
+
+func readInput(filename string) (res navi) {
+ file, _ := os.Open(filename)
+ defer file.Close()
+
+ actMap := map[byte]int{
+ 'N': N, 'S': S, 'E': E, 'W': W,
+ 'L': L, 'R': R, 'F': F,
+ }
+ scanner := bufio.NewScanner(file)
+ for scanner.Scan() {
+ row := scanner.Text()
+ res.act = append(res.act, actMap[row[0]])
+ val, _ := strconv.Atoi(row[1:])
+ res.val = append(res.val, val)
+ }
+ res.len = len(res.act)
+ return
+}
+
+func main() {
+ input := readInput("./input.txt")
+ // 796
+ fmt.Println(part(input, exec1))
+ // 39446
+ fmt.Println(part(input, exec2))
+}
+
+func rotate(dir int, act int, val int) int {
+ left := map[int]int{N: W, W: S, S: E, E: N}
+ right := map[int]int{N: E, E: S, S: W, W: N}
+ for i := 0; i < val/90; i++ {
+ if act == L {
+ dir = left[dir]
+ } else if act == R {
+ dir = right[dir]
+ }
+ }
+ return dir
+}
+
+func exec1(input navi) (x, y int) {
+ loc := map[int]int{}
+ dir := E
+ for i := 0; i < input.len; i++ {
+ act, val := input.get(i)
+ switch act {
+ case L, R:
+ dir = rotate(dir, act, val)
+ case F:
+ loc[dir] += val
+ default:
+ loc[act] += val
+ }
+ }
+ return loc[E] - loc[W], loc[N] - loc[S]
+}
+
+func exec2(input navi) (x, y int) {
+ loc := map[int]int{}
+ wpt := map[int]int{E: 10, N: 1}
+ for i := 0; i < input.len; i++ {
+ act, val := input.get(i)
+ switch act {
+ case L, R:
+ wpt = map[int]int{
+ rotate(N, act, val): wpt[N],
+ rotate(E, act, val): wpt[E],
+ rotate(S, act, val): wpt[S],
+ rotate(W, act, val): wpt[W],
+ }
+ case F:
+ for _, dir := range []int{N, E, S, W} {
+ loc[dir] += wpt[dir] * val
+ }
+ default:
+ wpt[act] += val
+ }
+ }
+ return loc[E] - loc[W], loc[N] - loc[S]
+}
+
+func abs(x int) int {
+ if x < 0 {
+ return -x
+ }
+ return x
+}
+
+func part(input navi, exec func(navi) (int, int)) int {
+ x, y := exec(input)
+ return abs(x) + abs(y)
+}