Package g0801_0900.s0818_race_car

Class Solution

java.lang.Object
g0801_0900.s0818_race_car.Solution
public class Solution extends java.lang.Object
818 - Race Car.

Hard

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 = 1Your 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.

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.

Constraints:

  • 1 <= target <= 104

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    racecar(int target)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • racecar

      public int racecar(int target)