Day 22 part 1.

22/answers.txt

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+4649
+¯\_(ツ)_/¯

22/input.txt

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+deal with increment 10
+cut -5908
+deal with increment 75
+cut 8705
+deal with increment 49
+cut -1609
+deal with increment 69
+cut 7797
+deal into new stack
+cut -6211
+deal with increment 10
+cut 6188
+deal with increment 57
+cut -1659
+deal with increment 16
+cut -5930
+deal into new stack
+cut -2758
+deal with increment 33
+cut -3275
+deal with increment 39
+cut -1301
+deal with increment 50
+cut 7837
+deal with increment 74
+cut 1200
+deal with increment 23
+deal into new stack
+cut -9922
+deal with increment 65
+cut 4896
+deal with increment 61
+deal into new stack
+cut 5945
+deal with increment 9
+deal into new stack
+deal with increment 2
+cut -8205
+deal with increment 75
+cut -4063
+deal with increment 40
+deal into new stack
+cut -7366
+deal with increment 51
+cut 7213
+deal into new stack
+cut 4763
+deal with increment 43
+cut 3963
+deal with increment 50
+cut -8856
+deal with increment 43
+cut 8604
+deal with increment 72
+cut -7026
+deal into new stack
+deal with increment 25
+cut 7843
+deal with increment 71
+cut -1272
+deal with increment 64
+cut 7770
+deal with increment 18
+cut -5278
+deal with increment 67
+deal into new stack
+deal with increment 18
+deal into new stack
+cut 2216
+deal with increment 42
+cut 3206
+deal with increment 14
+deal into new stack
+cut -6559
+deal into new stack
+deal with increment 12
+deal into new stack
+deal with increment 75
+deal into new stack
+deal with increment 41
+cut 7378
+deal with increment 44
+cut 774
+deal with increment 60
+cut 7357
+deal with increment 41
+cut 479
+deal with increment 40
+cut 5146
+deal with increment 13
+cut 2017
+deal into new stack
+deal with increment 35
+cut 9218
+deal into new stack
+deal with increment 22
+cut -2462
+deal with increment 23
+cut -1820
+deal with increment 69

22/main.go

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+package main
+
+import (
+	"fmt"
+	"github.com/csmith/aoc-2019/common"
+)
+
+func main() {
+	input := common.ReadFileAsStrings("22/input.txt")
+	deckSize := 10007
+	position := 2019
+	for _, line := range input {
+		var n int
+		if "deal into new stack" == line {
+			position = deckSize - 1 - position
+		} else if _, err := fmt.Sscanf(line, "cut %d", &n); err == nil {
+			n = (n + deckSize) % deckSize
+			if position < n {
+				position += deckSize - n
+			} else {
+				position -= n
+			}
+		} else if _, err := fmt.Sscanf(line, "deal with increment %d", &n); err == nil {
+			position = (position * n) % deckSize
+		} else {
+			panic(fmt.Sprintf("Unrecognised line: %s", line))
+		}
+	}
+	println(position)
+}