Day 12, part 1

 - Part 2 is so close, but there is something small missing in my corner
   detection...

Author: Björn Walter

12.py

@@ -0,0 +1,115 @@
+
+def extract_data(input):
+    """Extract"""
+    garden_map = []
+    with open(f"./input/{input}", 'r') as f:
+        lines = f.readlines()
+    for line in lines:
+        garden_map.append(line.strip())
+    return garden_map
+
+def get_clusters(matrix):
+    """Using a Depth-First search method."""
+    clusters = {}
+    visited = [[False for _ in range(len(matrix[0]))] for _ in range(len(matrix))]
+    directions = [(0,1), (0,-1), (1,0), (-1,0)]
+    
+    def dfs(i,j,cluster):
+        visited[i][j] = True
+        cluster.append((i,j))
+        for di, dj in directions:
+            ni, nj = i + di, j + dj
+            if 0 <= ni < len(matrix) and 0 <= nj < len(matrix[0]):
+                if not visited[ni][nj] and matrix[ni][nj] == matrix[i][j]:
+                    dfs(ni, nj, cluster)
+
+    for i in range(len(matrix)):
+        for j in range(len(matrix[0])):
+            if not visited[i][j]:
+                cluster = []
+                dfs(i,j,cluster)
+                value = matrix[i][j]
+                if value not in clusters:
+                    clusters[value] = []
+                clusters[value].append(cluster)
+    return clusters
+
+def get_region_cost(region):
+    directions = [(0,1), (0,-1), (1,0), (-1,0)]
+    fences = 0
+    region_size = len(region)
+    for coord in region:
+        #print(coord)
+        for di, dj in directions:
+            prox_coord = (coord[0] + di, coord[1] + dj)
+            if prox_coord not in region:
+                fences += 1
+    return fences * region_size
+
+def get_bulk_region_cost(region, matrix):
+    """Use a Moore-Neighbor tracing algorithm to find boundaries?"""
+    region_size = len(region)
+
+    # Amount of corners should be equal to sides. 
+    def find_corners(region):
+        outer_corners = []
+        inner_corners = []
+        for item in region:
+            i, j = item[0], item[1]
+            N = (i-1,j)
+            NW = (i-1,j-1)
+            W = (i,j-1)
+            SW = (i+1,j-1)
+            S = (i+1,j)
+            SE = (i+1,j+1)
+            E = (i, j+1)
+            NE = (i-1, j+1)
+            if N not in region and NW not in region and W not in region:
+                outer_corners.append(NW)
+            if S not in region and SW not in region and W not in region:
+                outer_corners.append(SW)
+            if S not in region and SE not in region and E not in region:
+                outer_corners.append(SE)
+            if N not in region and NE not in region and E not in region:
+                outer_corners.append(NE)
+            if N in region and E in region and (NE not in region):
+                inner_corners.append(item)
+            if S in region and E in region and (SE not in region):
+                inner_corners.append(item)
+            if S in region and W in region and (SW not in region):
+                inner_corners.append(item)
+            if N in region and W in region and (NW not in region):
+                inner_corners.append(item)
+        return len(outer_corners) + len(inner_corners)
+
+    corners = find_corners(region)
+
+    return corners* region_size
+
+    
+
+def part1():
+    garden_map = extract_data("12")
+    regions = get_clusters(garden_map)
+    score = 0
+    for region_type in regions:
+        for region in regions[region_type]:
+            cost = get_region_cost(region)
+            score += cost
+    
+    return score
+
+def part2():
+    garden_map = extract_data("12")
+    regions = get_clusters(garden_map)
+    score = 0
+    for region_type in regions:
+        for region in regions[region_type]:
+            cost = get_bulk_region_cost(region, garden_map)
+            score += cost
+    
+    return score
+
+if __name__ == "__main__":
+    print(f"Answer part 1: {part1()}")
+    print(f"Answer part 2: {part2()}")