ELEVTRBL - Elevator Trouble

You are on your way to your first job interview as a program tester, and you are already late. The interview is in a skyscraper and you are currently in floor s, where you see an elevator. Upon entering the elevator, you learn that it has only two buttons, marked "UP u" and "DOWN d". You conclude that the UP-button takes the elevator u floors up (if there aren't enough floors, pressing the UP-button does nothing, or at least so you assume), whereas the DOWN-button takes you d stories down (or none if there aren't enough). Knowing that the interview is at floor g, and that there are only f floors in the building, you quickly decide to write a program that gives you the amount of button pushes you need to perform. If you simply cannot reach the correct floor, your program halts with the message "use the stairs".

Given input f, s, g, u and d (floors, start, goal, up, down), find the shortest sequence of button presses you must press in order to get from s to g, given a building of floors, or output "use the stairs" if you cannot get from s to g by the given elevator.


The input will consist of one line, namely f s g u d, where 1 <= s, g <= f <= 1000000 and 0 <= u, d <= 1000000. The floors are one-indexed, i.e. if there are 10 stories, s and g be in [1; 10].


You must reply with the minimum numbers of pushes you must make in order to get from s to g, or output "use the stairs" if it is impossible given the conguration of the elevator.


10 1 10 2 1

100 2 1 1 0 

use the stairs

hide comments
vanvinhbk94: 2016-11-14 10:27:12

why runtime error (SIGSEGV) if use C++4.3.2 ... AC if use C++ 5.1 or C++ 14 ???

hung: 2016-10-05 04:37:40

Note s == g

prakash: 2016-09-23 17:24:11

some problems occur in size of array but finally solved it

flyingduchman_: 2016-08-14 14:21:58

In BFS , you should set "visited" array size to a big value like bool visited[10000000] to handle corner cases.

kunal todi: 2016-08-05 10:48:05

Can anyone let me know why after running 12 test cases successfully, the judge gives me wrong answer

Sachin Bisht : 2016-04-23 09:29:21

I am trying to implement this problem in JAVA but getting TLE.
Can anyone help me out. (FYI I am using ArrayDeque instead of LinkedList but still getting TLE)

try2catch: 2016-02-21 10:20:53

finally understood ! meaning of BFS.

chin: 2015-06-28 22:31:02

Finally AC..:D

Aditya Joshi: 2014-11-29 06:04:35


For people using Java, try and use an ArrayDeque instead of a LinkedList to implement your abstract Queue.

Last edit: 2014-11-29 06:04:45
chk: 2013-09-06 17:35:30

awesome problem :)

Added by:Krzysztof Lewko
Time limit:1s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ASM64
Resource:Nordic programming contest