Why doesn't my heapify work?

[Diez B. Roggisch]

Dongsheng Ruan wrote:

> I want to turn an Array into a heap, but my code just doesn't work: no
> change after execution.
> 
> A=[3,5,4,9,6,7]
> m=len(A)-1
> 
> 
> 
> for i in range(m,1):
>     t=(i-1)/2
>     if A[i]>A[t]:
>         A[i],A[t]=A[t],A[i]

First of all, there is the module heapq that will just do it.

And then you seem to misunderstand how the range-function works. range(m, 1)
will always be the empty list. See 

pydoc range

for how it operates.

Overall, your code is very unpythonic, to say the least. I suggest you start
reading the python tutorial first:

http://docs.python.org/tut/

Especially the looping techniques section:

http://docs.python.org/tut/node7.html#SECTION007600000000000000000

Diez