I want a really fast algorithm or code in C to do the following task: sum all numbers from 1 to N for any given integer N, without assuming N is positive. I made a loop summing from 1 to N, but it is too slow.
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I want a really fast algorithm or code in C to do the following task: sum all numbers from 1 to N for any given integer N, without assuming N is positive. I made a loop summing from 1 to N, but it is too slow.
If
Nis positive:int sum = N*(N+1)/2;If
Nis negative:int tempN = -N; int sum = 1 + tempN*(tempN+1)/2 * (-1);.