1 files changed, 166 insertions, 0 deletions
diff --git a/2019/go/day09.go b/2019/go/day09.go
new file mode 100644
index 0000000..432d780
--- /dev/null
+++ b/2019/go/day09.go
@@ -0,0 +1,166 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strconv"
+)
+
+func main() {
+	var memory []int
+	start, size := 0, 0
+	if len(os.Args) < 2 {
+		panic("runtime error: missing operand")
+	}
+	file, err := ioutil.ReadFile(os.Args[1])
+	if err != nil {
+		panic(err)
+	}
+	for i := 0; i < len(file); i++ {
+		if file[i] == ',' || file[i] == '\n' {
+			arg, err := strconv.Atoi(string(file[start:i])) // i-1??
+			if err != nil {
+				panic(err)
+			}
+			memory = append(memory, arg)
+			start = i + 1
+			size++
+		}
+	}
+	// fmt.Println(execute(memory, size))
+	// noun, verb := etucexe(memory, size, 19690720)
+	// fmt.Println(100*noun + verb)
+	execute(memory, size)
+}
+
+func split(memory []int, i, size, relative int) (int, int, int) {
+	mode := memory[i] / 100
+	three, two, one := i+3, i+2, i+1
+	if size-i > 1 {
+		if mode%10 == 0 {
+			one = memory[i+1]
+		} else if mode%10 == 2 {
+			one = relative + memory[i+1]
+		}
+		if size-i > 2 {
+			if mode/10%10 == 0 {
+				two = memory[i+2]
+			} else if mode%10 == 2 {
+				two = relative + memory[i+2]
+			}
+			if size-i > 3 {
+				if mode/100 == 0 {
+					three = memory[i+3]
+				} else if mode%10 == 2 {
+					three = relative + memory[i+3]
+				}
+			}
+		}
+	}
+	return three, two, one
+}
+
+func execute(memory []int, size int) []int {
+	/* todo: said "memory" functionality could be [pos, value]int
+	* i.e. when memory outside initial bounds wants to be accessed,
+	* it writes to a new element of this slice
+	* to access elements of the array, iterate through while checking each position
+	* additionally, to ensure there aren't conflicting "positions" in the array,
+	* do the above iteration process, if not, appends (this requires a total int)
+	 */
+	/*
+		var swap [][2]int
+	*/
+
+	// off-topic todo: https://www.golangprograms.com/example-arrays-of-arrays-arrays-of-slices-slices-of-arrays-and-slices-of-slices.html
+	// does this mean i can remove total / size because if so YES
+	for i := 0; i < 4000; i++ { // bad (example: no auto-termination due to 0 replacing nothingness)
+		memory = append(memory, 0)
+	}
+	relative := 0 // initial value of the relative base
+	for i := 0; i < len(memory); {
+		// bounds check
+		opcode := memory[i] % 100
+		three, two, one := split(memory, i, size, relative)
+		//fmt.Println("test:", opcode)
+		// actually what might work better than replacing all below would be
+		// checking if the next three values are out of bounds or not
+		// and then replacing them
+		// no bad idea large addition exists
+		switch opcode {
+		case 1: // adds
+			memory[three] = memory[one] + memory[two]
+			i += 4
+		case 2: // multiplies
+			// if out of bounds
+			// swap = append(swap, {memory[three], memory[one] * memory[two]})
+			// else
+			memory[three] = memory[one] * memory[two]
+			i += 4
+		case 3: // input
+			var input int
+			fmt.Print("Input: ")
+			resp, err := fmt.Scanf("%d", &input) // interesting note: anything following a valid integer is run by bash
+			if err != nil {
+				fmt.Println(resp, err)
+				os.Exit(0)
+			}
+			// out of bounds check
+			memory[one] = input // not affected by modes
+			i += 2
+		case 4: // output
+			fmt.Println(memory[one])
+			i += 2
+		case 5: // jump-if-true
+			if memory[one] != 0 {
+				i = memory[two]
+			} else {
+				i += 3
+			}
+		case 6: // jump-if-false
+			if memory[one] == 0 {
+				i = memory[two]
+			} else {
+				i += 3
+			}
+		case 7: // less than
+			if memory[one] < memory[two] {
+				memory[memory[i+3]] = 1 // instructions: _position_ given by the third parameter
+			} else {
+				memory[memory[i+3]] = 0
+			}
+			i += 4
+		case 8: // equals
+			if memory[one] == memory[two] {
+				memory[memory[i+3]] = 1
+			} else {
+				memory[memory[i+3]] = 0
+			}
+			i += 4
+		case 9: // adjusts the relative base
+			relative += memory[one] // interesting behavior when changing to i+1
+			i += 2
+		case 99: // terminate
+			return memory
+		default:
+			fmt.Println("Unsupported code", opcode, "at", i)
+			os.Exit(0)
+		}
+	}
+	return memory
+}
+
+func etucexe(memory []int, size, output int) (int, int) {
+	var volatile []int
+	for i := 0; i < len(memory); i++ {
+		for j := 0; j < len(memory); j++ {
+			volatile = append([]int(nil), memory...) // reset volatile to memory
+			volatile[1], volatile[2] = i, j
+			if execute(volatile, size)[0] == output {
+				return i, j
+			}
+		}
+	}
+	return -1, -1
+}