What is faster: many ifs, or else if?

Question

I\'m iterating through an array and sorting it by values into days of the week.

In order to do it I\'m using many if statements. Does it make any differ

Answer 1

If the values are integers you may achieve an optimisation by using a table lookup. E.g. say you have 256 values that map into 7 days somehow, you could set up an array with 256 cells and each cell contained the day of week you wanted. Then instead of:

if ( value == 0 ) {
  dayofweek = 1;
} else if ( value == 1 ) {
  dayofweek = 2;
} else if ( value == 2 ) {
  dayofweek = 3;
} else if ...

.. you could have..

dayofweek = lookuparray[value];

Of course, if you use this technique, then you should check the bounds of value first.