2021 day 13,15,16. need to clean up this code quite a bit

2021/day15/main.go

@@ -0,0 +1,173 @@
+package main
+
+import (
+	_ "embed"
+	"flag"
+	"fmt"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/cast"
+	"github.com/alexchao26/advent-of-code-go/data-structures/heap"
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+//go:embed input.txt
+var input string
+
+func init() {
+	// do this in init (not main) so test file has same input
+	input = strings.TrimRight(input, "\n")
+	if len(input) == 0 {
+		panic("empty input.txt file")
+	}
+}
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	if part == 1 {
+		ans := part1(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	} else {
+		ans := part2(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	}
+}
+
+func part1(input string) int {
+	grid := parseInput(input)
+	_ = grid
+
+	for i, rows := range grid {
+		for j := range rows {
+			if i == 0 && j == 0 {
+				continue
+			} else if i == 0 {
+				grid[i][j] += grid[i][j-1]
+			} else if j == 0 {
+				grid[i][j] += grid[i-1][j]
+			} else {
+				if grid[i-1][j] < grid[i][j-1] {
+					grid[i][j] += grid[i-1][j]
+				} else {
+					grid[i][j] += grid[i][j-1]
+				}
+			}
+		}
+	}
+	return grid[len(grid)-1][len(grid[0])-1] - grid[0][0]
+
+}
+
+func part2(input string) int {
+	// make the grid 5 times larger
+	// add 1 to every cell when moving right OR down (so diagonal is +2)
+	// 9 wraps back to 1
+	grid := parseInput(input)
+	bigGrid := make([][]int, len(grid)*5)
+	for i := range bigGrid {
+		bigGrid[i] = make([]int, len(grid[0])*5)
+	}
+	for r, row := range grid {
+		for c, v := range row {
+			bigGrid[r][c] = v
+		}
+	}
+
+	assignGrid := func(baseGrid [][]int, newGrid [][]int, r, c int) {
+		for i := 0; i < len(newGrid); i++ {
+			for j := 0; j < len(newGrid[0]); j++ {
+				baseGrid[r+i][c+j] = newGrid[i][j]
+			}
+		}
+	}
+
+	incrementGrid := func(baseGrid [][]int, by int) [][]int {
+		newGrid := make([][]int, len(baseGrid))
+		for i := range newGrid {
+			newGrid[i] = make([]int, len(baseGrid[0]))
+		}
+		for i := range baseGrid {
+			for j := range baseGrid[0] {
+				newGrid[i][j] = baseGrid[i][j] + by
+				for newGrid[i][j] > 9 {
+					newGrid[i][j] -= 9
+				}
+			}
+		}
+		return newGrid
+	}
+
+	for r := 0; r < 5; r++ {
+		for c := 0; c < 5; c++ {
+			if r == 0 && c == 0 {
+				continue
+			}
+			nextGrid := incrementGrid(grid, r+c)
+			assignGrid(bigGrid, nextGrid, r*len(grid), c*len(grid[0]))
+		}
+	}
+
+	minHeap := heap.NewMinHeap()
+	minHeap.Add(node{0, 0, 0})
+	visited := map[[2]int]bool{}
+	for minHeap.Length() > 0 {
+		front := minHeap.Remove().(node)
+		coord := [2]int{front.row, front.col}
+		// moving this check here instead of in the heap.Add() makes a HUGE difference
+		// by reducing the swell of the queue and following computations
+		if visited[coord] {
+			continue
+		}
+		visited[[2]int{front.row, front.col}] = true
+
+		if front.row == len(bigGrid)-1 && front.col == len(bigGrid[0])-1 {
+			return front.risk
+		}
+
+		// travel to all of front's neighbors
+		for _, d := range [][2]int{
+			{0, 1},
+			{1, 0},
+			{0, -1},
+			{-1, 0},
+		} {
+			nr, nc := front.row+d[0], front.col+d[1]
+			if nr >= 0 && nr < len(bigGrid) && nc >= 0 && nc < len(bigGrid[0]) {
+				minHeap.Add(node{
+					row:  nr,
+					col:  nc,
+					risk: front.risk + bigGrid[nr][nc],
+				})
+			}
+		}
+	}
+
+	panic("should return from loop")
+}
+
+// A* node
+type node struct {
+	row, col int
+	risk     int
+}
+
+func (n node) Value() int {
+	return n.risk
+}
+
+func parseInput(input string) (ans [][]int) {
+	for _, line := range strings.Split(input, "\n") {
+		var row []int
+		for _, char := range strings.Split(line, "") {
+			row = append(row, cast.ToInt(char))
+		}
+		ans = append(ans, row)
+	}
+	return ans
+}

2021/day15/main_test.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"testing"
+)
+
+var example = `1163751742
+1381373672
+2136511328
+3694931569
+7463417111
+1319128137
+1359912421
+3125421639
+1293138521
+2311944581`
+
+func Test_part1(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{
+			name:  "example",
+			input: example,
+			want:  40,
+		},
+		{
+			name:  "actual",
+			input: input,
+			want:  811,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part1(tt.input); got != tt.want {
+				t.Errorf("part1() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_part2(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{
+			name:  "example",
+			input: example,
+			want:  315,
+		},
+		{
+			name:  "actual",
+			input: input,
+			want:  3012,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part2(tt.input); got != tt.want {
+				t.Errorf("part2() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}