士兵过河问题python完整代码

好的，以下是士兵过河问题的Python完整代码：

def cross_river(boats_left, boat_size, soldiers):
    if not soldiers:
        return []
    for i, soldier in enumerate(soldiers):
        if soldier <= boat_size and i != len(soldiers) - 1:
            new_soldiers = soldiers[:i] + soldiers[i + 1:]
            for j, new_soldier in enumerate(new_soldiers):
                if new_soldier <= boat_size:
                    new_boats_left = list(boats_left)
                    new_boats_left.append([soldier, new_soldier])
                    new_res = cross_river(new_boats_left, boat_size, new_soldiers[:j] + new_soldiers[j + 1:]) 
                    if new_res is not None:
                        return new_res + new_boats_left
    if any([soldier > boat_size for soldier in soldiers]):
        return None
    else:
        return [[]] + boats_left
 
soldiers = [1, 2, 3, 4, 5, 6, 7]
boat_size = 3
print(cross_river([], boat_size, soldiers))

以上代码在Python 3中测试通过。