jamestomasino, add alternate solve for difficult day 12 (#77)

Author: jamestomasino

2024/12/jamestomasino.v

@@ -0,0 +1,139 @@
+import os
+
+struct Region {
+	id rune
+mut:
+	area      i64
+	perimeter []Perimeter
+	sides     []Perimeter
+}
+
+struct Perimeter {
+	p Point
+	d Vector
+}
+
+struct Point {
+	x int
+	y int
+}
+
+struct Vector {
+	dx int
+	dy int
+}
+
+fn is_valid_move(row int, col int, max_y int, max_x int) bool {
+	return row >= 0 && row < max_y && col >= 0 && col < max_x
+}
+
+fn check_cell(mut region &Region, mut visited [][]bool, grid []string, row int, col int, max_y int, max_x int) {
+	directions := [[0, 1], [0, -1], [1, 0], [-1, 0]]
+	for dir in directions {
+		new_row := row + dir[0]
+		new_col := col + dir[1]
+		// Is the new position on the grid
+		if is_valid_move(new_row, new_col, max_y, max_x) {
+			// Does new direction match our grid id
+			runes := grid[new_row].runes()
+			if runes[new_col] == region.id {
+				// Have we visited this before
+				if !visited[new_row][new_col] {
+					// add to region size
+					region.area += 1
+					// mark as visited
+					visited[new_row][new_col] = true
+					// recursive directional search
+					check_cell(mut region, mut visited, grid, new_row, new_col, max_y,
+						max_x)
+				}
+			} else {
+				// edge detected
+				region.perimeter << Perimeter{
+					p: Point{
+						y: row
+						x: col
+					}
+					d: Vector{
+						dy: dir[0]
+						dx: dir[1]
+					}
+				}
+			}
+		} else {
+			// grid border, add to perimeter
+			region.perimeter << Perimeter{
+				p: Point{
+					y: row
+					x: col
+				}
+				d: Vector{
+					dy: dir[0]
+					dx: dir[1]
+				}
+			}
+		}
+	}
+}
+
+fn main() {
+	grid := os.read_lines('garden.input')!
+
+	max_y := grid.len
+	max_x := grid[0].len
+
+	// initialize a 2D array to keep track of grid and visited elements
+	mut visited := [][]bool{len: max_y, init: []bool{len: max_x}}
+
+	// transverse grid
+	mut regions := []Region{}
+	for row in 0 .. max_y {
+		for col in 0 .. max_x {
+			// if element is unvisited:
+			if !visited[row][col] {
+				// identify new region and give it an identifier (char value)
+				visited[row][col] = true
+				runes := grid[row].runes()
+				mut region := &Region{
+					id:   runes[col]
+					area: 1
+				}
+				// check for each direction to see if 0) valid 1) unvisited and 2) matching id
+				check_cell(mut region, mut visited, grid, row, col, max_y, max_x)
+				regions << region
+			}
+		}
+	}
+
+	mut price := i64(0)
+	mut price2 := i64(0)
+	for mut r in regions {
+		price += r.area * r.perimeter.len
+
+		mut new_set := []Perimeter{}
+		for per in r.perimeter {
+			new_set << Perimeter{
+				p: Point{
+					y: per.p.y - per.d.dx
+					x: per.p.x + per.d.dy
+				}
+				d: per.d
+			}
+		}
+		r.sides = set_subtract(r.perimeter, new_set)
+		price2 += r.area * r.sides.len
+		// println('Region: ${r.id} (Area ${r.area}, Perimeter ${r.perimeter.len}, Sides ${r.sides.len})')
+	}
+	println('Part 1 total price: ${price}')
+	println('Part 2 total price: ${price2}')
+}
+
+fn set_subtract[T](set1 []T, set2 []T) []T {
+	mut result := []T{}
+	for item in set1 {
+		if !set2.contains(item) {
+			result << item
+		}
+	}
+	return result
+}

known/2024/12/jamestomasino.out

@@ -0,0 +1,2 @@
+Part 1 total price: 1930
+Part 2 total price: 1206