Felix Benner wrote:
> smartbei schrieb:
> > Hello, I am a newbie with python, though I am having a lot of fun using
> > it. Here is one of the excersizes I am trying to complete:
> > the program is supposed to find the coin combination so that with 10
> > coins you can reach a certain amoung, taken as a parameter. Here is the
> > current program:
> >
> > coins = (100,10,5,1,0.5)
> > anslist = []
> > def bar(fin, hist = {100:0,10:0,5:0,1:0,0.5:0}):
> > s = sum(x*hist[x] for x in hist)
> > l = sum(hist.values())
> > if s < fin and l < 10:
> > for c in coins:
> > if (s+c) <= fin:
> > hist[c] += 1
> > bar(fin, hist)
> > hist[c] -= 1
> > elif l==10 and s==fin and not hist in anslist:
> > #p1
> > anslist.append(hist)
> >
> > bar(50)
> > print anslist
> >
> > The problem is that if I run it, anslist prints as [{0.5: 0, 1: 0, 10:
> > 0, 100: 0, 5: 0}], which doesnt even add up to 50. When I check how
> > many times the program has reached the #p1 by sticking a print there,
> > it only reaches it once, and it comes out correct. why is it that this
> > result is replaced by the incorrect final one?
> >
>
> hist is stored in anslist as a pointer only, therfore the hist[c] -= 1
> operates on the same dict as is stored in the anslist. Try the following
> in the python interpreter:
>
> a = { 'key' : 1 }
> l = [a]
> l[0]['key'] -= 1
> a
>
> instead use:
>
> anslist.append(dict(hist.items))
>
> which will copy the dict.
Thanks!
BTW - its hist.items(), after that it worked.
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