This is indeed nice… but I presume that we all agree that the best solution
here would be to allow instantiation of an IntSummaryStatistics object in a
specific state.
> On Mar 29, 2017, at 2:43 PM, Peter Levart <peter.lev...@gmail.com> wrote:
>
>
>
> On 03/29/2017 06:06 PM, Chris Dennis wrote:
>> Remi: I really have to squint pretty hard to see that as anything other than
>> “brute-force” - it’s still an O(N) calculation.
>
> Here's O(log2(N)):
>
> static IntSummaryStatistics create(long count, long sum, int min, int max)
> {
> if (count < 2 || min == max) {
> return combineProduct(new IntSummaryStatistics(), count, min);
> } else {
> long minCnt = (count * max - sum) / (max - min);
> long maxCnt = count - minCnt - 1;
> long minSum = minCnt * min;
> long maxSum = maxCnt * max;
> long minMaxSum = minSum + maxSum;
> int mid = (int) (sum - minMaxSum);
> IntSummaryStatistics stats = new IntSummaryStatistics();
> combineProduct(stats, minCnt, min);
> combineProduct(stats, maxCnt, max);
> stats.accept(mid);
> return stats;
> }
> }
>
> static IntSummaryStatistics combineProduct(IntSummaryStatistics stats,
> long count, int value) {
> IntSummaryStatistics pow2 = null;
> while (count > 0) {
> if (pow2 == null) {
> pow2 = new IntSummaryStatistics();
> pow2.accept(value);
> } else {
> pow2.combine(pow2);
> }
> if ((count & 1L) == 1L) {
> stats.combine(pow2);
> }
> count >>>= 1;
> }
> return stats;
> }
>
>
> Regards, Peter
>
