day7_compact.py

def evaluate_expression(nums, ops):
    r = nums[0]
    for i, op in enumerate(ops):
        if op == '+': r += nums[i + 1]
        elif op == '*': r *= nums[i + 1]
        else: r = r * (10 ** len(str(nums[i + 1]))) + nums[i + 1]
    return r

def can_make_equation_part1(tv, nums):
    def try_combs(pos, ops):
        if pos == len(nums) - 1: return evaluate_expression(nums, ops) == tv
        for op in ['+', '*']:
            ops.append(op)
            if try_combs(pos + 1, ops): return True
            ops.pop()
        return False
    return try_combs(0, [])

def can_make_equation_part2(tv, nums):
    def try_combs(pos, ops, curr):
        if pos == len(nums) - 1: return curr == tv
        n = nums[pos + 1]
        for op, fn in [('+', lambda x,y: x+y), ('*', lambda x,y: x*y), 
                      ('||', lambda x,y: x*(10**len(str(y)))+y)]:
            ops.append(op)
            if (new := fn(curr, n)) <= tv and try_combs(pos + 1, ops, new): return True
            ops.pop()
        return False
    return try_combs(0, [], nums[0])

def solve_calibration(data, part2=False):
    return sum(tv for line in data.strip().split('\n')
              if (tv := int(line.split(': ')[0]))
              and (can_make_equation_part2 if part2 else can_make_equation_part1)
              (tv, [int(x) for x in line.split(': ')[1].split()]))

if __name__ == "__main__":
    try:
        with open('day7.data') as f:
            data = f.read()
            for part2 in [False, True]:
                print(f"Part {1 if not part2 else 2}: {solve_calibration(data, part2)}")
    except FileNotFoundError:
        print("Error: day7.data not found")