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<p>我已经在Java和Python中实现了一个简单的算法来计算给定斜边长度的所有勾股三元组。出于某种原因,Python实现所需的时间要长约20倍。为什么会这样?你知道吗</p>
<pre><code>$ time python PythagoreanTriples.py
[2800, 9600, 3520, 9360, 5376, 8432, 6000, 8000, 8000, 6000, 8432, 5376, 9360, 3520, 9600, 2800]
python PythagoreanTriples.py 13.92s user 0.71s system 87% cpu 16.698 total
$ time java PythagoreanTriples
[2800, 9600, 3520, 9360, 5376, 8432, 6000, 8000, 8000, 6000, 8432, 5376, 9360, 3520, 9600, 2800]
java PythagoreanTriples 0.32s user 0.12s system 72% cpu 0.618 total
</code></pre>
<p>算法是将<code>a</code>和<code>b</code>值按<code>a</code>值的升序和<code>b</code>值的降序添加到输出列表中。下面是Python和Java程序。你知道吗</p>
<p>Python:</p>
<pre><code>def pythagorean_triples(c):
"""
:param c: the length of the hypotenuse
:return: a list containing all possible configurations of the other two
sides that are of positive integer length. Output each
configuration as a separate element in a list in the format a b
where a is in ascending order and b is in descending order in
respect to the other configurations.
"""
output = []
c_squared = c * c
for a in xrange(1, c):
a_squared = a * a
for b in xrange(1, c):
b_squared = b * b
if a_squared + b_squared == c_squared:
output.append(a)
output.append(b)
return output
</code></pre>
<p>爪哇语:</p>
<pre><code>public static Iterable<Integer> findTriples(int hypotenuse) {
ArrayList<Integer> output = new ArrayList<Integer>();
int c_2 = hypotenuse * hypotenuse;
for(int a = 1; a < hypotenuse; a++) {
int a_2 = a * a;
for(int b = 1; b < hypotenuse; b++) {
int b_2 = b * b;
if(a_2 + b_2 == c_2) {
output.add(a);
output.add(b);
}
}
}
return output;
}
</code></pre>