day10/solution_claude-3-5-sonnet-20241022.py

from collections import defaultdict
from typing import List, Set, Tuple, Dict

def read_grid(filename: str) -> List[List[int]]:
    with open(filename) as f:
        return [[int(c) for c in line.strip()] for line in f]

def get_neighbors(grid: List[List[int]], x: int, y: int) -> List[Tuple[int, int]]:
    directions = [(0, 1), (1, 0), (0, -1), (-1, 0)]
    height, width = len(grid), len(grid[0])
    neighbors = []
    for dx, dy in directions:
        nx, ny = x + dx, y + dy
        if 0 <= nx < height and 0 <= ny < width:
            neighbors.append((nx, ny))
    return neighbors

def find_trailheads(grid: List[List[int]]) -> List[Tuple[int, int]]:
    return [(i, j) for i in range(len(grid)) for j in range(len(grid[0])) if grid[i][j] == 0]

def count_reachable_nines(grid: List[List[int]], start: Tuple[int, int]) -> int:
    def dfs(x: int, y: int, visited: Set[Tuple[int, int]]) -> Set[Tuple[int, int]]:
        nines = set()
        visited.add((x, y))
        current_height = grid[x][y]
        
        if current_height == 9:
            nines.add((x, y))
            
        for nx, ny in get_neighbors(grid, x, y):
            if (nx, ny) not in visited and grid[nx][ny] == current_height + 1:
                nines.update(dfs(nx, ny, visited))
                
        return nines
    
    return len(dfs(start[0], start[1], set()))

def count_distinct_paths(grid: List[List[int]], start: Tuple[int, int]) -> int:
    memo: Dict[Tuple[int, int], int] = {}
    
    def dfs(x: int, y: int) -> int:
        if (x, y) in memo:
            return memo[(x, y)]
        
        if grid[x][y] == 9:
            return 1
            
        paths = 0
        current_height = grid[x][y]
        
        for nx, ny in get_neighbors(grid, x, y):
            if grid[nx][ny] == current_height + 1:
                paths += dfs(nx, ny)
                
        memo[(x, y)] = paths
        return paths
    
    return dfs(start[0], start[1])

def solve_part1(grid: List[List[int]]) -> int:
    trailheads = find_trailheads(grid)
    return sum(count_reachable_nines(grid, start) for start in trailheads)

def solve_part2(grid: List[List[int]]) -> int:
    trailheads = find_trailheads(grid)
    return sum(count_distinct_paths(grid, start) for start in trailheads)

grid = read_grid("./input.txt")
print(str(solve_part1(grid)))
print(str(solve_part2(grid)))