如何找到N no的最接近值 进入序列？

Question

I have a list of integer sequence:

[10,15,30,45,60,75,90......n*15]

Let's say you have a value ie 33 What calculation i should do to find the closest value of 33 into the above sequence? (JavaScript) Can we find it without loop?

Thanks.

Answer 1

As others have already pointed out, if you're working with multiples of 15 (assuming the sequence starting with 10 was a mistake), then you can simply do the following:

 var interval = 15; var value = 33; var closest = Math.round(value / interval) * interval; console.log(closest); 

Answer 2

You didn't specify any language, so here is some pseudocode. Also I assume that the sequence is actually 15*n and there has to be 0 instead of 10 as the first element. Assume the sequence is form 0 to 15*N and the test value is test . IMHO, the simplest algorithm is following:

if(test <= 0) 
      return 0
else if (test >= 15*N)
      return 15*N
else {
   lower = Math.floor(test/15)
   upper = lower + 1
   lowerDif = test - 15*lower
   upperDif = 15*upper - test
   if (lowerDif < upperDif) 
      return 15*lower
   else
      return 15*upper
}

The idea is that you need to check if test is inside [0; 15*N] [0; 15*N] range. If no - return the boundary, else check two values at indices Math.floor(test/15) and Math.floor(test/15) + 1 . It is true that

    Math.floor(test/15) <= test < Math.floor(test/15) + 1

So whichever is closer is the answer.