Day 13.

13/answers.txt

@@ -0,0 +1,2 @@
+432
+22225

13/main.go

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"github.com/csmith/aoc-2019/common"
+	"github.com/csmith/aoc-2019/intcode"
+)
+
+func patch(input []int, width int) {
+	// Insert two quarters
+	input[0] = 2
+
+	// Find the bottom line of the play area and change it to wall
+	for i := len(input) - 1; i > 0; i-- {
+		if input[i] == 1 && input[i-width] == 1 {
+			allEmpty := true
+			for j := i - width + 1; j < i-1; j++ {
+				if input[j] != 0 {
+					allEmpty = false
+					break
+				}
+			}
+
+			if allEmpty {
+				for j := i - width + 1; j < i-1; j++ {
+					input[j] = 1
+				}
+				break
+			}
+		}
+	}
+}
+
+func feedInput(input chan int) {
+	for {
+		input <- 0
+	}
+}
+
+func readOutput(output chan int, handler func(int, int, int)) {
+	for {
+		x, more := <-output
+		if !more {
+			break
+		}
+		y := <-output
+		tile := <-output
+		handler(x, y, tile)
+	}
+}
+
+func countBlocks(screen [60][80]int) (blocks int) {
+	for _, line := range screen {
+		for _, pixel := range line {
+			if pixel == 2 {
+				blocks++
+			}
+		}
+	}
+	return
+}
+
+func run(input []int, handler func(int, int, int)) {
+	memory := make([]int, len(input))
+	copy(memory, input)
+	vm := intcode.NewVirtualMachine(memory)
+	vm.Input = make(chan int, 1)
+	vm.Output = make(chan int, 6)
+
+	go feedInput(vm.Input)
+	go vm.Run()
+
+	readOutput(vm.Output, handler)
+}
+
+func main() {
+	input := common.ReadCsvAsInts("13/input.txt")
+	memory := make([]int, len(input))
+	copy(memory, input)
+
+	width := 0
+	var screen [60][80]int
+	run(memory, func(x int, y int, tile int) {
+		screen[y][x] = tile
+		if x > width {
+			width = x
+		}
+	})
+
+	println(countBlocks(screen))
+
+	patch(input, width)
+
+	score := 0
+	run(input, func(x int, y int, tile int) {
+		if x == -1 {
+			score = tile
+		}
+	})
+
+	println(score)
+}