meetaig - 9 months ago 35

Python Question

I have a function that reads a file byte by byte and converts it to a floating point array. It also returns the number of elements in said array.

Now I want to reshape the array into a 2D array with the shape being as close to a square as possible.

As an example let's look at the number 800:

`sqrt(800) = 28.427...`

Now by I can figure out by trial and error that

`25*32`

I do this by decrementing the

`sqrt`

I know about algorithms that do this for primes, but this is not a requirement for me. My problem is that even the brute force method I implemented will sometimes get stuck and never finish (which is the reason for my arbitrary limit of iterations):

`import math`

def factor_int(n):

nsqrt = math.ceil(math.sqrt(n))

factors = [nsqrt, nsqrt]

cd = 0

result = factors[0] * factors[1]

ii = 0

while (result != n or ii > 10000):

if(result > n):

factors[cd] -= 1

else:

factors[cd] += 1

result = factors[0] * factors[1]

print factors, result

cd = 1 - cd

ii += 1

return "resulting factors: {0}".format(factors)

input = 80000

factors = factor_int(input)

using this script above the output will get stuck in a loop printing

`[273.0, 292.0] 79716.0`

[273.0, 293.0] 79989.0

[274.0, 293.0] 80282.0

[274.0, 292.0] 80008.0

[273.0, 292.0] 79716.0

[273.0, 293.0] 79989.0

[274.0, 293.0] 80282.0

[274.0, 292.0] 80008.0

[273.0, 292.0] 79716.0

[273.0, 293.0] 79989.0

[274.0, 293.0] 80282.0

[274.0, 292.0] 80008.0

[273.0, 292.0] 79716.0

[273.0, 293.0] 79989.0

[274.0, 293.0] 80282.0

[274.0, 292.0] 80008.0

[273.0, 292.0] 79716.0

[273.0, 293.0] 79989.0

[274.0, 293.0] 80282.0

But I wonder if there are more efficient solutions for this? Certainly I can't be the first to want to do something like this.

Answer

```
def factor_int(n):
nsqrt = math.ceil(math.sqrt(n))
solution = False
val = nsqrt
while not solution:
val2 = int(n/val)
if val2 * val == float(n):
solution = True
else:
val-=1
return val, val2, n
```

try it with:

```
for x in xrange(10, 20):
print factor_int(x)
```

Source (Stackoverflow)