I would do `print 5050;` ;-)
In response to the original post, you don't need to be a mathematician to know this. I heard about this formula in elementary school, with an anecdote supposedly involving Carl Friedrich Gauss and a nasty math teacher.
Regarding the "programmer/mathematician" comparison, be careful, because sometimes you see naive "mathematicians" that:
- suggest a wonderful but extremely complicated O(N) algorithm, without noticing that for a given aplication N is always between 0 and 2, and considering the overhead, the N^2 method is actually faster.
- don't care about the implementation issues of the language they are using, so they use a theoretically pretty but unnecessary recursive implementation that ends up being too slow or resource-intensive.
The point that thinking is sometimes better than brute force is well taken, but sometimes the opposite is good enough or better. From the Jargon File:
Ken Thompson, co-inventor of Unix, is reported to have uttered the epigram *"When in doubt, use brute force"*. He probably intended this as a ha ha only serious, but the original Unix kernel's preference for simple, robust, and portable algorithms over brittle 'smart' ones does seem to have been a significant factor in the success of that OS. Like so many other tradeoffs in software design, the choice between brute force and complex, finely-tuned cleverness is often a difficult one that requires both engineering savvy and delicate esthetic judgment.
| [reply] [d/l] |

`my sum = 100 * 101 / 2;
`
or something like that.
I know this from practice, as I once accidentally wrote
8092 instead of 32*256 in a program and
had a hard time finding out why it wouldn't work.
A computer can do arithmetic better than any of us.
| [reply] [d/l] |

I did it with a computer...in the shape of a calculator:)
I get your point, but unless the constants 100, 101 and 2 have some meaning in context, you've just advocated magic numbers.
A well named constant, that made sense in context, would be preferable.
Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"Think for yourself!" - Abigail
"Memory, processor, disk in that order on the hardware side. Algorithm, algorithm, algorithm on the code side." - tachyon
| [reply] |

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