Race Car

Description

Your car starts at position 0 and speed +1 on an infinite number line. Your car can go into negative positions. Your car drives automatically according to a sequence of instructions 'A' (accelerate) and 'R' (reverse):

- When you get an instruction 'A', your car does the following:



- position += speed

- speed *= 2





- When you get an instruction 'R', your car does the following:


- If your speed is positive then speed = -1

- otherwise speed = 1



Your position stays the same.

For example, after commands "AAR", your car goes to positions 0 --> 1 --> 3 --> 3, and your speed goes to 1 --> 2 --> 4 --> -1.

Given a target position target, return the length of the shortest sequence of instructions to get there.