12-2

2024/12/12-2.py

@@ -0,0 +1,124 @@
+width = height = 0
+map = {}
+
+def printMap():
+    output = ""
+    for i in range(height):
+        line = ""
+        for j in range(width):
+            line += map[j,i]
+        output += line + "\n"
+    print(output)
+
+def findNeighbours(node):
+    x, y = node
+    nodes = set()
+    directions = [(1, 0), (0, 1), (-1, 0), (0, -1)]
+    for direction in directions:
+        dirX, dirY = direction
+        neighbour = (x + dirX, y + dirY)
+        if neighbour in map:
+            nodes.add(neighbour)
+    return nodes
+
+# the number of edges should be the same as the number of corners in the shape
+# this assertion should be true even if a region is wholly wrapping another
+# say it's wrapping a square, that would just add 4 edges due to the squares 4 corners
+# will need to get a mechanism for both interior and exterior facing corners
+def findCorners(region):
+    corners = 0
+    for node in region:
+        testedNodes = set()
+        char = map[node]
+        # if both neighbours are not this node's value, that's an exterior corner
+        # else, using pairs neighbour nodes: if both match, have those neighbours check the shared cell that isn't this node
+        # if that cell is different, that's an interior corner
+
+        x, y = node
+        # do left + top/bottom, the right + top/bottom
+        topAndBottom = leftAndRight = [-1, 1]
+
+        for lr in leftAndRight:
+            dirX = lr
+            lr = (x + lr, y)
+            for tb in topAndBottom:
+                dirY = tb
+                tb = (x, y + tb)
+                # if one's OoB and one's in, if the one that's in is different value,
+                # we have an internal corner
+                if lr not in map and tb not in map:
+                    #corner of the map
+                    corners += 1
+                    continue
+
+                if lr in map and tb not in map:
+                    if map[lr] != map[node]:
+                        corners += 1
+                    continue
+                elif lr not in map and tb in map:
+                    if map[tb] != map[node]:
+                        corners += 1
+                    continue
+
+                # we know they're in bounds due to checks above
+                if tb in region and lr in region:
+                    diagonal = (x + dirX, y + dirY)
+                    if diagonal not in testedNodes and map[diagonal] != map[node]:
+                        testedNodes.add(diagonal)
+                        # external corner
+                        corners += 1
+                elif tb not in region and lr not in region:
+                    #internal corner
+                    corners += 1
+    return corners
+
+def getRegion(node):
+    region = set() # set is like dict but I don't have to do that stupid (x,y): True thing I was doing
+    checkedNodes = set()
+    # do BFS or something
+    uncheckedNeighbours = [node]
+    while len(uncheckedNeighbours) != 0:
+        node = uncheckedNeighbours[0]
+        region.add(node)
+        checkedNodes.add(node)
+        # get neighbours
+        # add them to list if they have the same character
+
+        neighbourCandidates = findNeighbours(node)
+        unvisitedNeighbours = [neighbour for neighbour in neighbourCandidates if (map[neighbour] == map[node] and neighbour not in checkedNodes and neighbour not in uncheckedNeighbours)]
+        uncheckedNeighbours += unvisitedNeighbours
+        del uncheckedNeighbours[0]
+
+    return region
+
+with open("2024/12/input.txt") as f:
+    for i, line in enumerate(f):
+        line = line.strip()
+        if i == 0:
+            width = height = int(len(line))
+        for j, char in enumerate(line):
+            map[j,i] = char
+
+printMap()
+
+visitedNodes = set()
+regions = []
+totalCost = 0
+
+for i in range(height):
+    for j in range(width):
+        node = (i, j)
+        if node not in visitedNodes:
+            # region finding
+            newRegion = getRegion(node)
+            regions.append(newRegion)
+            visitedNodes |= newRegion
+
+            # costs
+            area = len(newRegion)
+            edges = findCorners(newRegion)
+            cost = area * edges
+            totalCost += cost
+            print(f'{map[list(newRegion)[0]]}: {cost}')
+
+print(totalCost)