Problem:
Assume given sequence :
2,3,4,5,6,8,9,10,12,15…
All these numbers are multiples of either 2 , 3, or 5 (and no other numbers).
Find the nth element of this sequence. (This is the interview question in flipkart)
Solution:
This can be thought in recursive terms. But to begin with, we can clearly see, 2.5=10 is part of series, but 2.7=14 is not part of series. So, while generation of numbers we have to make sure that divisor is not part of numbers like 7,11,13 etc.
Java code
public int GetNumberFromSequence(int n)
{
if(n==1)
return 2;
if(n>1)
for(int i=1;;i++)
{
int possibleNumber=GetNumberFromSequence(n-1)+i;
if(IsAllowedNumber(possibleNumber))
return possibleNumber;
else
continue;
}
}
public bool IsAllowedNumber(int possibleNumber)
{
for(int n: primesExcept\_2\_3\_5 )
if(possibleNumber%n == 0)
return false;
else
if(n>possibleNumber)
return true;
}
Thanks