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Covid Run Codechef October long challenge problem solution| Codechef October long challenge problem solution

Covid Run Codechef October long  challenge problem solution| Codechef October long  challenge problem solution -

This is very first and easy problem of Codechef October long  challenge problem solution| Codechef October long  challenge problem solution.

Problem Statement-

Covid-19 is spreading fast! There are N cities, numbered from 0 to (N1), arranged in a circular manner. City 0 is connected to city 11 to 2, city (N2) to city (N1), and city (N1) to city 0.

The virus is currently at city X. Each day, it jumps from its current city, to the city K to its right, i.e., from city X to the city (X+K)%N. As the virus jumps, the cities in between don't get infected. Cities once infected stay infected. You live in city YFind if it will reach your city eventually. If it will, print YES, else print NO.


  • The first line of the input consists of an integer T, the number of test cases.
  • The first and only line of each test case contains four space-separated integers - NKX and Y, denoting the number of cities, the size of jumps, Covid's current city, and the city that you live in, respectively.


For each test case, in a new line, print YES if Covid shall reach your city after a finite number of days, else print NO.


  • 1T100
  • 1N1000
  • 0X,YN1
  • 0K1000


  • Subtask 1 - 100% - Original constraints

Sample Input:

6 2 5 3
12 3 4 2

Sample Output:



  • In the first sample, Covid starts at city 5, then goes to city 1, and then from city 1 to city 3. Thus, it reaches the city that you live in.

  • In the second sample, Covid starts at city 4, goes to city 7, then 101, then 4710, and so on. It never reaches city 2.

Let's directly jump into solution 
according to problem statement take input t= total number of test cases .
next line contain n,k,xand y
take input for n,k,x and y.
virus is currently at city x.
spreading rate of virus is k means virus can jump k city from its currenty position x.
Question says that you are living currently at y city so you have to tell that virus may infect you or not.

Approach of this question is very simple simply you have to jump k step from current city and if this goes out of (N-1) city  it will 
return back to city (n+k)%n th city.

dont try to think too much follow steps as mentioned in question it is called bruete force approach.

My approach-

My approach says that if the virus currently at city x in the next step it will jump to (x+k)%n th city.
What i will do i will maintain a  flag variable that will tell me that virus can reach to place y or not.

step 1-If virus already at position y. so i have to simply return true.otherwise, I will move form current city to x+k th this case i will mark my flag as true and terminate the loop.
step 2- if virus reach again at x position it mean it will never reach to city y and the person who is sitting in city y is safe.
in this case i will mark my flag as false and terminate the loop.

finally, i will print the result according to the flag


Entire code solution is given below-


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