84 lines
2.2 KiB
Python
84 lines
2.2 KiB
Python
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#!/usr/bin/env python
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# 2024 - Advent Of Code 6 - part 2
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# file = 'input_example.txt'
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file = 'input.txt'
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input_lines = []
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with open(file, encoding="utf-8") as f:
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for l in f.readlines():
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input_lines.append(list(l.strip()))
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MAX_X = len(input_lines[0])
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MAX_Y = len(input_lines)
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vector=(0, 0)
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gx = 0
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gy = 0
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for y in range(0, MAX_Y):
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for x in range(0, MAX_X):
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g = input_lines[y][x]
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if g not in ('.', '#'):
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gx = x
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gy = y
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print(f'found guard at {x}, {y}')
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if g == '^':
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vector = (0, -1)
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if g == 'v':
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vector = (0, 1)
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if g == '>':
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vector = (1, 0)
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if g == '<':
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vector = (-1, 0)
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print(f'{vector=}')
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moves = [(0,-1), (1, 0), (0, 1), (-1, 0)]
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move = moves.index(vector)
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def move_and_detect(grid, posx, posy, v, m):
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visited = [(posx, posy, v)]
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while 0 < posx < MAX_X and 0 < posy < MAX_Y:
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nx = posx + v[0]
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ny = posy + v[1]
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if nx < 0 or nx >= MAX_X or ny < 0 or ny >= MAX_Y:
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return False
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if grid[ny][nx] != '#':
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posx += v[0]
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posy += v[1]
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if (posx, posy, v) in visited:
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return True
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visited.append((posx, posy, v))
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else:
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m += 1
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v = moves[m % 4]
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return False
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start_gx = gx
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start_gy = gy
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start_vector = vector
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start_move = move
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found_loop = set()
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while 0 <= gx < MAX_X and 0 <= gy < MAX_Y:
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nextx = gx + vector[0]
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nexty = gy + vector[1]
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if nextx < 0 or nextx >= MAX_X or nexty < 0 or nexty >= MAX_Y:
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break
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if input_lines[nexty][nextx] != '#':
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# print(f'testing bloc at {nextx}, {nexty}')
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old_value = input_lines[nexty][nextx]
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input_lines[nexty][nextx] = '#'
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if (nextx, nexty) not in found_loop:
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if move_and_detect(input_lines, start_gx, start_gy, start_vector, start_move):
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print(f'found loop with bloc at {nextx}, {nexty}')
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found_loop.add((nextx, nexty))
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input_lines[nexty][nextx] = old_value
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gx = nextx
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gy = nexty
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else:
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move += 1
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vector = moves[move % 4]
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# print(f'new vector: {vector}')
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print(f'{len(found_loop)=}')
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