added part 2, not happy with it

day8/main.go

@@ -7,6 +7,28 @@ import (
 	"strings"
 )
 
+func run(p program) (acc int, err error) {
+	ip := 0           // Instruction Pointer
+	a := 0            // Accumulator "register"
+	for ip < len(p) { // while we're still in the program
+		i := &p[ip] // instruction at pointer
+		i.Executions = i.Executions + 1
+		if i.Executions == 2 {
+			return a, fmt.Errorf("Early exit input:%d", ip-1)
+		}
+		switch i.Op {
+		case "nop":
+			ip += 1
+		case "jmp":
+			ip += i.Arg
+		case "acc":
+			a += i.Arg
+			ip += 1
+		}
+	}
+	return a, nil
+}
+
 type instruction struct {
 	Executions int // Execution count
 	Arg        int
@@ -26,24 +48,22 @@ func main() {
 			p = append(p, instruction{Arg: n, Op: f[0]})
 		}
 	}
-	ip := 0           // Instruction Pointer
-	a := 0            // Accumulator "register"
-	for ip < len(p) { // while we're still in the program
-		i := &p[ip] // instruction at pointer
-		fmt.Println(i)
-		i.Executions = i.Executions + 1
-		if i.Executions == 2 {
-			fmt.Println(a)
-			return
+	working := make(program, len(p))
+	copy(working, p)
+	o, _ := run(working)
+	fmt.Println("Part 1: ", o)
+	for i, v := range p {
+		working := make(program, len(p))
+		copy(working, p)
+		if v.Op == "nop" {
+			working[i].Op = "jmp"
+		} else if v.Op == "jmp" {
+			working[i].Op = "nop"
 		}
-		switch i.Op {
-		case "nop":
-			ip += 1
-		case "jmp":
-			ip += i.Arg
-		case "acc":
-			a += i.Arg
-			ip += 1
+		a, err := run(working)
+		if err == nil {
+			fmt.Println("Part 2: ", a)
+			return
 		}
 	}
 }