advent_of_code/9/9.py

#!/usr/bin/env python
# 2021 - Advent Of Code - 9

def parse_file(file):
    hmap = []
    with open(file) as f:
        for line in f.readlines():
            linemap = []
            for n in line.strip():
                linemap.append(int(n))
            hmap.append(linemap)

    return hmap


def print_hmap(hmap):
    for y, _ in enumerate(hmap):
        for x, _ in enumerate(hmap[y]):
            print(hmap[y][x], end='')
        print()


def find_lowpoints(hmap):
    lpoints = []

    # first line
    x = 0
    y = 0
    if hmap[y][x] < hmap[y][x + 1] and hmap[y][x] < hmap[y + 1][x]:
        lpoints.append([x, y])

    for x in range(1, len(hmap[y]) - 1):
        v = hmap[y][x]
        if v < hmap[y][x - 1] and v < hmap[y][x + 1] and v < hmap[y + 1][x]:
            lpoints.append([x, y])

    x = len(hmap[y]) - 1
    if hmap[y][x] < hmap[y][x - 1] and hmap[y][x] < hmap[y + 1][x]:
        lpoints.append([x, y])

    # middle lines
    for y in range(1, len(hmap) - 1):
        x = 0
        if hmap[y][x] < hmap[y][x + 1] and hmap[y][x] < hmap[y - 1][x] and hmap[y][x] < hmap[y + 1][x]:
            lpoints.append([x, y])

        for x in range(1, len(hmap[y]) - 1):
            v = hmap[y][x]
            if v < hmap[y][x - 1] and v < hmap[y][x + 1] and v < hmap[y - 1][x] and v < hmap[y + 1][x]:
                lpoints.append([x, y])

        x = len(hmap[y]) - 1
        if hmap[y][x] < hmap[y][x - 1] and hmap[y][x] < hmap[y - 1][x] and hmap[y][x] < hmap[y + 1][x]:
            lpoints.append([x, y])

    # last line
    y = len(hmap) - 1
    x = 0
    if hmap[y][x] < hmap[y][x + 1] and hmap[y][x] < hmap[y - 1][x]:
        lpoints.append([x, y])

    for x in range(1, len(hmap[y]) - 1):
        v = hmap[y][x]
        if v < hmap[y][x - 1] and v < hmap[y][x + 1] and v < hmap[y - 1][x]:
            lpoints.append([x, y])

    x = len(hmap[y]) - 1
    if hmap[y][x] < hmap[y][x - 1] and hmap[y][x] < hmap[y - 1][x]:
        lpoints.append([x, y])

    return lpoints


# heightmap = parse_file('input_example.txt')
heightmap = parse_file('input.txt')
# print_hmap(heightmap)
low_points = find_lowpoints(heightmap)

risk_levels = 0
for p in low_points:
    print(f'low point at {p}, value {heightmap[p[1]][p[0]]}')
    risk_levels += heightmap[p[1]][p[0]] + 1

print(f'The sum of risk levels is {risk_levels}')