check if the two sum is even number and get the numbers
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To clarify, you mean to count how many pairs of numbers that, when added together, are even? Are these integers or decimals too?
If these are all integers, do one pass to count how many even and odd numbers there are.
Every 2 even numbers added is even, and same for odds, so do combinations. A and B be the counts of even and odds so that the final answer is
A*(A-1) / 2 + B*(B-1)/2
This is O(n) since it requires only one pass through the array.
Yes. The sum of any 2 even or 2 odd numbers is even.
- Miguel Oliveira July 10, 2014