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.
Now for some target position, say the length of the shortest sequence of instructions to get there.
Example 1: Input: target = 3 Output: 2 Explanation: The shortest instruction sequence is "AA". Your position goes from 0>1>3.
Example 2: Input: target = 6 Output: 5 Explanation: The shortest instruction sequence is "AAARA". Your position goes from 0>1>3>7>7>6.
Note:

1 <= target <= 10000
.