Advent of Code 2023 Day 14

Author

Nathan Moore

— Day 14: Parabolic Reflector Dish —

There are some rocks on a platform which some mirrors are sitting on, but the platform is a bit broken.

Tilt the platform so that the rounded rocks all roll north. Afterward, what is the total load on the north support beams?

with open('data-2023-14.txt', 'r') as f:
    inp = f.read().splitlines()

Maybe write an explanation of the solution approach here

import numpy as np

rocks = np.array([list(i) for i in inp])

for m in range(len(rocks)): 
    for n in range(len(rocks[m,:])): 
        # makes me feel better to explicitly mention these
        if rocks[m,n] == '.' or rocks[m,n] == '#':
            pass
        # this is the main part of the thing
        else: 
            p = m
            while True: 
                # cannot move up from the top or into another rock 
                if p == 0 or rocks[p-1,n] == 'O' or rocks[p-1,n] == '#':
                    break
                else: 
                    rocks[p-1,n] = 'O'
                    rocks[p,n] = '.'
                    p -= 1

# for m in rocks:
#     print(''.join(m))

summer = 0

for m in range(len(rocks)):
    # print(m)
    # print(''.join(rocks[m]).count('O'))
    summer += ''.join(rocks[m]).count('O') * (len(rocks)-m)
  
summer

— Part Two —

We need to move the platform around to make sure it is not too broken.

Run the spin cycle for 1000000000 cycles. Afterward, what is the total load on the north support beams?

rocks = np.array([list(i) for i in inp])
    
def go_north(): 
    for m in range(len(rocks)): 
        for n in range(len(rocks[m,:])): 
            # makes me feel better to explicitly mention these
            if rocks[m,n] == '.' or rocks[m,n] == '#':
                pass
            # this is the main part of the thing
            else: 
                p = m
                while True: 
                    # cannot move up from the top or into another rock 
                    if p == 0 or rocks[p-1,n] == 'O' or rocks[p-1,n] == '#':
                        break
                    else: 
                        rocks[p-1,n] = 'O'
                        rocks[p,n] = '.'
                        p -= 1
                  
                        
def go_south(): 
    for m in range(len(rocks)-1, -1, -1): 
        for n in range(len(rocks[m,:])): 
            # makes me feel better to explicitly mention these
            if rocks[m,n] == '.' or rocks[m,n] == '#':
                pass
            # this is the main part of the thing
            else: 
                p = m
                while True: 
                    if p == len(rocks)-1 or rocks[p+1,n] == 'O' or rocks[p+1,n] == '#':
                        break
                    else: 
                        rocks[p+1,n] = 'O'
                        rocks[p,n] = '.'
                        p += 1    


def go_west(): 
    for m in range(len(rocks)): 
        for n in range(len(rocks[m,:])): 
            # makes me feel better to explicitly mention these
            if rocks[m,n] == '.' or rocks[m,n] == '#':
                pass
            # this is the main part of the thing
            else: 
                p = n
                while True: 
                    if p == 0 or rocks[m,p-1] == 'O' or rocks[m,p-1] == '#':
                        break
                    else: 
                        rocks[m,p-1] = 'O'
                        rocks[m,p] = '.'
                        p -= 1
                        
def go_east(): 
    for m in range(len(rocks)): 
        for n in range(len(rocks[m,:])-1, -1, -1): 
            # makes me feel better to explicitly mention these
            if rocks[m,n] == '.' or rocks[m,n] == '#':
                pass
            # this is the main part of the thing
            else: 
                p = n
                while True: 
                    if p == len(rocks)-1 or rocks[m,p+1] == 'O' or rocks[m,p+1] == '#':
                        break
                    else: 
                        rocks[m,p+1] = 'O'
                        rocks[m,p] = '.'
                        p += 1                        


# north, then west, then south, then east
for c in range(1000): 
# for c in range(1000000000):   
    go_north()
    # for m in rocks:
    #     print(''.join(m))
    # print()        
    go_west()
    # for m in rocks:
    #     print(''.join(m))
    # print()        
    go_south()
    # for m in rocks:
    #     print(''.join(m))
    # print()        
    go_east()
    # for m in rocks:
    #     print(''.join(m))
    # print()        
    summer = 0
    for m in range(len(rocks)):
        summer += ''.join(rocks[m]).count('O') * (len(rocks)-m)
    # summer

# for m in rocks:
#     print(''.join(m))


# summer = 0
# for m in range(len(rocks)):
#     summer += ''.join(rocks[m]).count('O') * (100-m)
# summer

# manually inspect this output from 1000 iterations
# repeating sequence of length 52, starting at position 87

# 1000000000 % 52
(1000000000-2) % 7
(1000000000-86) % 52

# 100183 too low 
# 100184 too low
# 100310