114 lines
3.2 KiB
Python
114 lines
3.2 KiB
Python
#!/usr/bin/env python
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# https://adventofcode.com/2025/day/10
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from itertools import combinations, product
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from sympy import symbols, Matrix, solve_linear_system
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f = open("day10input.txt", "r")
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# regular input
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input = f.readlines()
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# testinput
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#input = "[.##.] (3) (1,3) (2) (2,3) (0,2) (0,1) {3,5,4,7}\n[...#.] (0,2,3,4) (2,3) (0,4) (0,1,2) (1,2,3,4) {7,5,12,7,2}\n[.###.#] (0,1,2,3,4) (0,3,4) (0,1,2,4,5) (1,2) {10,11,11,5,10,5}".split("\n")
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machines = []
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for input_line in input:
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line = input_line.rstrip("\n").split(" ")
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machine = {}
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# final state
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fs = line[0][1:-1].replace(".", "0").replace("#", "1")
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machine["fs"] = int(fs, base=2)
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# switches
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switches = []
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for switch in line[1:-1]:
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s = ["0"] * len(fs)
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for i in [int(j) for j in switch[1:-1].split(",")]:
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s[i] = "1"
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switches.append("".join(s))
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machine["s"] = sorted([int(s, base=2) for s in switches], key=int.bit_count)
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# joltage req's
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machine["j"] = [int(n) for n in line[-1][1:-1].split(",")]
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machines.append(machine)
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def print_machines(machines: list[dict]) -> None:
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for i in range(len(machines)):
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print(f"Machine no. {i}")
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for k in machines[i].keys():
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print(f"key:\t{k}\tvalue:\t{machines[i][k]}")
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def part1_bfs(m):
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for steps in range(1, len(m["s"])):
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# check if current step no yields a solution
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for c in list(combinations(m["s"], steps)):
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lights = 0
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for i in c:
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lights ^= i
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if lights == m["fs"]:
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print(f"Success with combo {i} and step count of {steps}")
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return steps
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return None
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def part2(m):
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switches = [list(map(int, list("{0:b}".format(switch).zfill(len(m["j"]))))) for switch in m["s"]]
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joltages = m["j"]
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# define sympy symbols and equations
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x = symbols(f"x:{len(switches)}", integer=True)
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system = Matrix([[switch[j] for switch in switches] + [joltages[j]] for j in range(len(joltages))])
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print(f"Equation system to solve: {system}")
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# solve system with sympy
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solutions = solve_linear_system(system, *x)
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print(f"Solutions: {solutions}")
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# isolate free variables
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free_vars = [var for var in x if var not in solutions.keys()]
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print(f"{free_vars=}")
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# find smallest solution
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smallest_sum = None
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# loop over the cartesian product of sensible numbers for button presses times the number of free variables
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for lv in product(range(max(joltages)), repeat=len(free_vars)):
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# print(f"{lv=}")
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current_sum = sum(lv)
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for v in solutions.values():
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for i in range(len(lv)):
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v = v.subs(free_vars[i], lv[i])
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# print(f"{v=}")
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if v < 0:
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# print(f"negative button press number for {lv=} -> skipping")
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current_sum = -1
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break
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current_sum += v
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if current_sum < 0:
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continue
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# print(f"-> {current_sum=}")
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# check current sum
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if not current_sum.is_Integer:
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continue
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elif not smallest_sum or current_sum < smallest_sum:
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smallest_sum = current_sum
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print(f"Smallest number of presses found: {smallest_sum}")
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return smallest_sum
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#print_machines(machines)
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#print(sum(list(map(part1_bfs, machines))))bin
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steps = 0
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for machine in machines:
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steps += part2(machine)
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print(f"current total step number: {steps}")
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print(f"final total step number: {steps}")
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