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ELEVSTRS - Editorial

PROBLEM LINK:

Practice
Contest

Author: Yuri Shilyaev
Tester: Hasan Jaddouh
Editorialist: Yury Shilyaev

DIFFICULTY:

CAKEWALK

PREREQUISITES:

Equation of uniform motion.

PROBLEM:

You are given two variants of route, one with length equal to $sqrt(2) * N$ and maximal velocity $V_1$, and another with length equal to $2 \cdot N$ and maximal velocity $V_2$. You have to find which route will use less time.

QUICK EXPLANATION:

$S = v * t$, so just calculate time of both routes.
The complexity is $O(1)$ for one testcase, $O(T)$ in total.

EXPLANATION:

Time of the first route is $T_1 = \frac{sqrt(2) * N}{ V_1}$. Time of the second $T_2 = \frac{2 * N}{V_2}$.
So, we can compare this fractional numbers, or, alternatively, make some transitions and get that:

$T_1$ ? $T_2$

$V_2 * sqrt(2)$ ? $V_1 * 2$

$V_2$ ? $V_1 * sqrt(2)$

So, the first route is faster if $V_2 < V_1 * sqrt(2)$. Why the times couldn't be equal? Imagine that $V_2 = V_1 * sqrt(2)$. $V_2$ is integer, while $V_1 * sqrt(2)$ is irrational. Obviously, they can't be equal.

AUTHOR'S AND TESTER'S SOLUTIONS:

Author's solution can be found here.
Tester's solution can be found here.

RELATED PROBLEMS:

This question is marked "community wiki".

asked 20 Aug '17, 18:22

hloya_ygrt's gravatar image

4★hloya_ygrt
119
accept rate: 0%

edited 21 Aug '17, 00:25

admin's gravatar image

0★admin ♦♦
19.8k350498541


include <iostream>

include<cmath>

include<string>

using namespace std;

int main() { int t,n,v1,v2; string str1="Elevator"; string str2="Stairs"; cin>>t; while(t--) { cin>>n>>v1>>v2; if(v2>(v1*sqrt(2))) cout<<str1<<"\n"; else cout<<str2<<"\n"; }strong text

return 0;

}

link

answered 21 Aug '17, 07:57

avishek_1997's gravatar image

1★avishek_1997
1
accept rate: 0%

//package codechef4; import java.io.; import java.util.;

class Solution {

public static void main(String[] args) {
    // TODO Auto-generated method stub

Scanner sc = new Scanner (System.in);

int t = sc.nextInt();
for(int j = 0 ; j < t ; j ++) {

    int n = sc.nextInt();
    double v1 = sc.nextDouble();
    double v2 = sc.nextDouble();

    double t1=0,t2=0;
    t1 = ((Math.sqrt(2) * n)/v1);
    //System.out.println(t1);

    t2 = (2 * n)/v2;
    //System.out.println(t2);

    String res = t1 < t2 ? "Stairs" : "Elevator";

    System.out.println(res);

}

}

}

link

answered 29 Aug '17, 00:09

jigar_786's gravatar image

1★jigar_786
1
accept rate: 0%

include <iostream.h>

using namespace std; int main() { cout<<"hey"; return 0; }

link

answered 07 Sep '17, 19:11

sundeep1234's gravatar image

0★sundeep1234
1
accept rate: 0%

Hi

I'm new to code chef recently joined.

I'm trying to solve the elevator problem .Howeve rwhen I submit I keep getting wrong answer error.

Please help!! here's my code:

int main(){

int distance = 0, vel1 = 0, vel2 = 0; float time1 = 0 ,time2 =0;

//Enter Distance, velocity of elevator and stairs scanf("%d %d %d",&distance,&vel1,&vel2);

/if vel1>vel2 i.e velocity of stairs velocity of Elevator automatically display stairs since 1.41Distance < 2Distance/

if(vel1 >= vel2){ printf("Stairs"); return(0); }

time1 = (sqrt(2) * distance)/ (float) vel1; time2 = (2*distance)/(float) vel2; //convert to float

//Check for least time if(time1 <time2) printf("Stairs"); else printf("Elevator");

return(0); }

link

answered 20 Feb '18, 15:52

jenya's gravatar image

0★jenya
22
accept rate: 0%

edited 20 Feb '18, 15:55

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question asked: 20 Aug '17, 18:22

question was seen: 1,480 times

last updated: 20 Feb '18, 15:55