I'm pretty new to python, but am very happy with it. As well as using
it at work I've been using it to solve various puzzles on the Project
Euler site - http://projecteuler.net. So far it has not let me down,
but it has proved surprisingly slow on one puzzle.
The puzzle is: p is the perimeter of a right angle triangle with
integral length sides, {a,b,c}. which value of p < 1000, is the
number of solutions {a,b,c} maximised?
Here's my python code:
#!/usr/local/bin/python
solutions = [0] * 1001
p = 0
for a in xrange(1, 1000):
for b in xrange(1, 1000 - a):
for c in xrange(1, 1000 - a - b):
p = a + b + c
if p < 1000:
if a ** 2 + b ** 2 == c ** 2:
solutions[p] += 1
max = 0
maxIndex = 0
index = 0
for solution in solutions:
if solution > max:
max = solution
maxIndex = index
index += 1
print maxIndex
It takes 2 minutes and twelve seconds on a 2.4GHz Core2Duo MacBook
Pro. Surprised at how slow it was I implemented the same algorithm in
C:
#include <stdio.h>
#include <stdlib.h>
int main() {
int* solutions = calloc(1000, sizeof(int));
int p;
for(int a = 1; a < 1000; ++a) {
for(int b = 1; b < 1000 - a; ++b) {
for(int c = 1; c < 1000 - a - b; ++c) {
p = a + b + c;
if(p < 1000) {
if(a * a + b * b == c * c) {
solutions[p] += 1;
}
}
}
}
}
int max = 0;
int maxIndex = 0;
for(int i = 0; i < 1000; ++i) {
if(solutions[i] > max) {
max = solutions[i];
maxIndex = i;
}
}
printf("%d\n", maxIndex);
return 0;
}
gcc -o 39 -std=c99 -O3 39.c
The resulting executable takes 0.24 seconds to run. I'm not expecting
a scripting language to run faster than native code, but I was
surprised at how much slower it was in this case. Any ideas as to what
is causing python so much trouble in the above code?
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