main.go

package main

import (
	"fmt"
	"strconv"
	"strings"

	"github.com/mbark/advent-of-code-2020/util"
)

var input = `
acc +17
acc +37
acc -13
jmp +173
nop +100
acc -7
jmp +447
nop +283
acc +41
acc +32
jmp +1
jmp +585
jmp +1
acc -5
nop +71
acc +49
acc -18
jmp +527
jmp +130
jmp +253
acc +11
acc -11
jmp +390
jmp +597
jmp +1
acc +6
acc +0
jmp +588
acc -17
jmp +277
acc +2
nop +163
jmp +558
acc +38
jmp +369
acc +13
jmp +536
acc +38
acc +39
acc +6
jmp +84
acc +11
nop +517
acc +48
acc +47
jmp +1
acc +42
acc +0
acc +2
acc +24
jmp +335
acc +44
acc +47
jmp +446
nop +42
nop +74
acc +45
jmp +548
jmp +66
acc +1
jmp +212
acc +18
jmp +1
acc +4
acc -16
jmp +366
acc +0
jmp +398
acc +45
jmp +93
acc +40
acc +38
acc +21
nop +184
jmp -46
nop -9
jmp +53
acc +46
acc +36
jmp +368
acc +16
acc +8
acc -9
acc -4
jmp +328
acc -15
acc -5
acc +21
jmp +435
acc -5
acc +36
jmp +362
acc +26
jmp +447
jmp +1
jmp +412
acc +11
acc +41
nop -32
acc +17
jmp -63
jmp +1
nop +393
jmp +62
acc +18
acc +30
nop +417
jmp +74
acc +29
acc +23
jmp +455
jmp +396
jmp +395
acc +33
nop +137
nop +42
jmp +57
jmp +396
acc +7
acc +0
jmp +354
acc +15
acc +50
jmp -12
jmp +84
nop +175
acc +5
acc -2
jmp -82
acc +1
acc +26
jmp +288
nop -113
nop +366
acc +45
jmp +388
acc +21
acc +38
jmp +427
acc +33
jmp -94
nop -118
nop +411
jmp +472
nop +231
nop +470
acc +48
jmp -124
jmp +1
acc +5
acc +37
acc +42
jmp +301
acc -11
acc -17
acc +14
jmp +357
acc +6
acc +20
acc +13
jmp +361
jmp -65
acc +29
jmp +26
jmp +329
acc +32
acc +32
acc +17
jmp -102
acc -6
acc +33
acc +9
jmp +189
acc +3
jmp -128
jmp -142
acc +24
acc -5
jmp +403
acc +28
jmp +310
acc +34
acc +4
acc +33
acc +18
jmp +227
acc -8
acc -15
jmp +112
jmp +54
acc +21
acc +23
acc +20
jmp +320
acc +13
jmp -77
acc +15
nop +310
nop +335
jmp +232
acc -3
nop +50
acc +41
jmp +112
nop -10
acc +29
acc +27
jmp +52
acc +40
nop -132
acc -16
acc +27
jmp +309
acc -8
nop +147
acc +20
acc +46
jmp +202
acc +27
jmp -43
jmp +1
acc +33
acc -13
jmp +300
acc +1
jmp -202
acc -17
acc +0
acc +34
jmp -5
nop +335
acc -16
acc -17
jmp -120
acc -19
acc -13
acc +4
jmp +368
jmp +21
acc +39
acc +39
acc -18
jmp -157
nop +280
acc +33
nop -37
jmp +32
acc -16
acc +18
acc +46
jmp -121
acc -19
jmp +195
acc +28
jmp +124
jmp +331
jmp -228
jmp -146
jmp +85
jmp +60
acc +20
acc -9
jmp +303
jmp -122
jmp +111
acc +32
acc +0
acc +39
acc +29
jmp -31
nop +320
jmp -63
jmp +223
nop -149
acc -12
acc -11
acc +32
jmp +309
jmp -13
acc -19
jmp -123
acc +21
acc +18
acc +49
jmp +175
acc -14
nop -129
acc -2
acc +31
jmp +79
acc +23
acc +50
acc +39
acc +7
jmp -235
jmp -166
acc +9
jmp +293
acc -11
jmp +76
acc +44
acc +3
acc +37
jmp +123
nop -104
jmp -157
acc +14
acc +10
acc +28
jmp +25
acc +37
jmp +188
jmp -49
acc -11
jmp -90
acc -8
jmp +197
acc +5
jmp +115
acc +44
jmp -228
nop -2
acc +46
jmp +130
nop +183
nop +106
acc +27
acc +37
jmp -309
acc +28
acc -4
acc -12
acc +38
jmp +93
acc +8
acc +23
acc -9
acc +6
jmp -42
acc +10
acc +35
acc +4
jmp -231
acc +19
acc +7
acc +23
acc +11
jmp -90
acc +0
nop +158
nop -150
acc +33
jmp +107
acc +48
acc -2
jmp -104
acc +6
nop -57
nop +172
acc -11
jmp -7
acc +6
acc +50
acc -9
acc +12
jmp -171
acc +3
jmp +26
acc +42
acc +31
acc +20
acc +32
jmp -48
acc +13
jmp -6
jmp +178
acc +47
jmp -153
acc +28
nop +74
jmp -162
acc -15
nop -104
acc -9
jmp -227
acc +49
acc -19
acc +41
jmp -318
acc +9
acc +12
acc +7
jmp +34
jmp +137
nop -143
acc -8
acc +5
acc +31
jmp -20
jmp -237
acc +39
acc +0
jmp -298
acc +45
acc -19
acc +11
jmp -151
acc +40
acc +27
nop +150
nop -391
jmp -341
acc +1
acc +11
acc +18
nop -234
jmp +77
nop +104
jmp -65
acc +32
jmp -27
nop -317
nop +159
acc +14
acc -10
jmp -348
acc +29
jmp +32
acc +48
acc -19
jmp +17
jmp -201
jmp -224
nop +26
acc -7
acc +23
acc +46
jmp -6
acc +22
acc +39
acc +9
acc +23
jmp -30
jmp -243
acc +47
acc -15
jmp -298
jmp -393
jmp +1
acc +3
nop -24
acc +7
jmp -59
acc -6
acc +26
jmp -102
acc +34
acc +24
jmp -207
acc +36
acc +40
acc +41
jmp +1
jmp -306
jmp +57
jmp +1
nop +99
acc +28
jmp -391
acc +50
jmp -359
acc -5
jmp +9
jmp -355
acc +5
acc +2
jmp -77
acc +40
acc +28
acc +22
jmp -262
nop -287
acc +34
acc -4
nop +112
jmp -195
acc +29
nop -94
nop -418
jmp +24
jmp -190
acc +2
jmp -311
jmp -178
jmp -276
acc -12
acc -18
jmp +62
jmp -174
nop +31
acc +33
nop -158
jmp -417
acc +3
acc +21
acc +47
jmp +87
acc +45
jmp -77
acc +6
acc -10
jmp +1
jmp -240
acc +7
acc +47
jmp -379
acc -14
acc +50
nop -75
acc +30
jmp +70
jmp -392
jmp -430
acc +22
acc -2
jmp -492
jmp +1
acc -6
acc +38
jmp -36
nop -336
jmp -32
jmp +61
acc +20
acc -9
acc +2
jmp -175
acc +21
acc -2
jmp -6
jmp -527
acc +11
acc +16
jmp -262
jmp +1
nop -327
acc +29
jmp -114
acc +11
acc +17
acc +26
nop -104
jmp -428
nop -178
nop -242
acc +29
acc +5
jmp -245
jmp -417
jmp -278
acc +35
acc +21
jmp +1
nop -263
jmp +8
acc +42
jmp -95
nop -312
acc -11
acc +34
acc +0
jmp +19
acc +8
acc -13
acc +32
acc +21
jmp -208
acc +15
acc +39
nop -194
jmp -280
jmp +24
nop -516
acc +21
acc +48
jmp -367
jmp -121
acc +49
acc -16
jmp -136
acc +0
jmp -148
jmp -85
jmp -103
nop -446
jmp -242
acc -12
acc +13
acc +31
acc -1
jmp -435
nop -420
acc +22
acc -5
jmp -567
nop -354
acc +11
acc +33
acc +45
jmp -76
acc -2
acc +0
acc +25
acc +46
jmp -555
acc +0
acc +11
nop -2
jmp -394
jmp -395
acc +8
acc +14
acc +47
acc +22
jmp +1
`

var testInput = `
nop +0
acc +1
jmp +4
acc +3
jmp -3
acc -99
acc +1
jmp -4
acc +6
`

type Instruction struct {
	Op  string
	Inc int
}

func main() {
	lines := util.ReadInput(input, "\n")

	var instructions []Instruction
	for _, l := range lines {
		s := strings.Split(l, " ")
		op := s[0]

		var inc int
		if strings.HasPrefix(s[1], "+") {
			inc, _ = strconv.Atoi(s[1][1:])
		} else {
			inc, _ = strconv.Atoi(s[1][1:])
			inc = inc * -1
		}

		instructions = append(instructions, Instruction{Op: op, Inc: inc})
	}

	fmt.Printf("first %d\n", first(instructions))
	fmt.Printf("second %d\n", second(instructions))
}

func first(instructions []Instruction) int {
	_, acc := execute(instructions)
	return acc
}

func second(instructions []Instruction) int {
	for i := range instructions {
		var newIns *Instruction

		op := instructions[i].Op
		if op == "nop" {
			newIns = &Instruction{Op: "jmp", Inc: instructions[i].Inc}
		} else if op == "jmp" {
			newIns = &Instruction{Op: "nop", Inc: instructions[i].Inc}
		}

		if newIns == nil {
			continue
		}

		newInstructions := append([]Instruction{}, instructions...)
		newInstructions[i] = *newIns

		done, acc := execute(newInstructions)
		if done {
			return acc
		}
	}

	panic("no instruction found")
}

func execute(instructions []Instruction) (bool, int) {
	visisted := make(map[int]bool)
	idx := 0

	acc := 0
	for {
		if idx == len(instructions) {
			return true, acc
		}

		visisted[idx] = true
		ins := instructions[idx]

		switch ins.Op {
		case "nop":
			idx += 1
		case "acc":
			acc += ins.Inc
			idx += 1
		case "jmp":
			idx += ins.Inc
		}

		if _, ok := visisted[idx]; ok {
			break
		}
	}

	return false, acc
}