Anyway, lets get started with Problem 1. Of course, the basic solution is simple: walk over the numbers between 0 and 1000, check whether 3 or 5 divides it, add them to the sum. I figured I could play with some efficiency, but it turned out (clicky) that there is simply an x86 operator that does the modular operation, so there's not a whole lot to speed up here. Here's what I did in C:
#include
int main(){
int i = 0;
int sum=0;
while (i<1000){
if ((i%3==0) | (i%5==0)){
sum+=i;
}
i++;
}
printf("%d\n",sum);
}
I'm kind of bothered by the fact that I need the include. But anyway, you can also do this without a division if you really want it. it's easiest to demonstrate with python:
rresult=0
for i in range(999,0,-3):
result+=i
for i in range(995,0,-5):
result+=i
for i in range(15,1000,15):
result-=i
print result
Of course, these numbers are pretty boring. I tried to scale things up a bit, so I modified the C code to use longs for the sum and had both go up to 1 000 000. Using memtime (a little tool to record time and used memory for whatever you feed it), I recorded the time each took. As expected, python is way slower:
namnatulco@namnatulco-desktop:~/codestuff$ memtime ./a.out
233333166668
Exit [0]
0.01 user, 0.00 system, 0.10 elapsed -- Max VSize = 1616KB, Max RSS = 56KB
namnatulco@namnatulco-desktop:~/codestuff$ memtime python test.py
233333166668
Exit [0]
0.27 user, 0.00 system, 0.40 elapsed -- Max VSize = 12472KB, Max RSS = 8544KB
However, if I change the python code to match what the C code does, this happens:
namnatulco@namnatulco-desktop:~/codestuff$ memtime python test.py
233333166668
Exit [0]
0.74 user, 0.00 system, 0.80 elapsed -- Max VSize = 7212KB, Max RSS = 3312KB
Surprising? Perhaps at first, yes. But if you know a little bit about python, you'll know it has a lot of C in the background. Looks like even though the range() function takes a large amount of memory, it's way faster than manual computation.
So that's it. Enough toying with code; go listen to this magnificent post-hardcore album:
There's a sample track (Vulgar Theories) for listening on the dischord website (take note: flash).
