2016-day8: rotating rows & cols of a 2D grid

2016/day08/main.go

@@ -0,0 +1,89 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	count, finalString := twoFA(util.ReadFile("./input.txt"), 6, 50)
+	if part == 1 {
+		fmt.Println("Output:", count)
+	} else {
+		fmt.Println("Output:")
+		fmt.Println(finalString)
+	}
+}
+
+func twoFA(input string, height, width int) (int, string) {
+	instructions := strings.Split(input, "\n")
+	var grid [][]bool
+	for i := 0; i < height; i++ {
+		grid = append(grid, make([]bool, width))
+	}
+
+	for _, inst := range instructions {
+		if strings.HasPrefix(inst, "rect") {
+			var row, col int
+			fmt.Sscanf(inst, "rect %dx%d", &col, &row)
+			for r := 0; r < row; r++ {
+				for c := 0; c < col; c++ {
+					grid[r][c] = true
+				}
+			}
+		} else if strings.HasPrefix(inst, "rotate row") {
+			var row, by int
+			_, err := fmt.Sscanf(inst, "rotate row y=%d by %d", &row, &by)
+			if err != nil {
+				panic("parsing error on instruction: " + err.Error())
+			}
+			for count := 0; count < by; count++ {
+				store := grid[row][width-1]
+				for i := width - 1; i > 0; i-- {
+					grid[row][i] = grid[row][i-1]
+				}
+				grid[row][0] = store
+			}
+		} else if strings.HasPrefix(inst, "rotate column") {
+			var col, by int
+			_, err := fmt.Sscanf(inst, "rotate column x=%d by %d", &col, &by)
+			if err != nil {
+				panic("parsing error on instruction: " + err.Error())
+			}
+			for count := 0; count < by; count++ {
+				store := grid[height-1][col]
+				for r := height - 1; r > 0; r-- {
+					grid[r][col] = grid[r-1][col]
+				}
+				grid[0][col] = store
+			}
+		} else {
+			panic("unhandled instruction: " + inst)
+		}
+	}
+
+	var count int
+	var finalState string
+	// count on pixels
+	for _, row := range grid {
+		for _, v := range row {
+			if v {
+				finalState += "#"
+				count++
+			} else {
+				finalState += " "
+			}
+		}
+		finalState += "\n"
+	}
+
+	return count, finalState
+}