pgoultiaev/aoc2017

package main

type stateInstruction struct {
    writeVal0, writeVal1         int
    cursorChange0, cursorChange1 int
    nextState0, nextState1       string
}

var (
    A = stateInstruction{1, 0, 1, -1, "B", "D"}
    B = stateInstruction{1, 0, 1, 1, "C", "F"}
    C = stateInstruction{1, 1, -1, -1, "C", "A"}
    D = stateInstruction{0, 1, -1, 1, "E", "A"}
    E = stateInstruction{1, 0, -1, 1, "A", "B"}
    F = stateInstruction{0, 0, 1, 1, "C", "E"}

    states = map[string]stateInstruction{"A": A, "B": B, "C": C, "D": D, "E": E, "F": F}
)

func main() {
    println(solve(12302209, states))
}

func solve(diagnoseAfter int, states map[string]stateInstruction) (checksum int) {
    t := map[int]int{}
    currentState := "A"

    cursor := 0
    i := 0
    for i < diagnoseAfter {
        cursorChange, nextState, writeVal := evalState(currentState, t[cursor], states)
        t[cursor] = writeVal
        cursor += cursorChange
        currentState = nextState
        i++
    }

    for k := range t {
        if t[k] == 1 {
            checksum++
        }
    }

    return checksum
}

func evalState(state string, cursorVal int, states map[string]stateInstruction) (cursorChange int, nextState string, writeVal int) {
    s := states[state]
    if cursorVal == 0 {
        return s.cursorChange0, s.nextState0, s.writeVal0
    }
    return s.cursorChange1, s.nextState1, s.writeVal1
}