Glitch in python code when converted from C++ code?

Question

I'm kind of new to python, and I wonder how you would convert the following code in C++ to python

int kids, cd;
while (cin >> kids >> cd){
    if (kids == 0 && cd == 0)
    break;
    cout << pow(cd, kids)<<endl;
}

So I think it's probably something like

    from math import pow
    kids = int(raw_input())
    cd = int(raw_input())
    while kids!=0 and cd!=0:
       print pow(cd, kids)
       kids = int(raw_input())
       cd = int(raw_input())

When I submit my python code to the online judge SPOJ, I got a runtime error. My C++ code isn't accepted because of the overflow when the numbers get too large... What's wrong?

Also when I tried to compile the python code using

http://repl.it/languages/Python

with input

2
5

and I get the output

25.0

But how do I make it to be 25 instead of 25.0?

Thanks!

@Hugh: >> is probably intentional; cin >> x reads from the standard input into x. — icktoofay
– icktoofay, Commented Jan 31, 2014 at 3:43
Yes, >> is intentional; on each line, there will be two variables kids and cd to be read in — user3213711
– user3213711, Commented Jan 31, 2014 at 3:47

icktoofay · Accepted Answer · 2014-01-31 03:52:48Z

Your Python code is close to, but not quite like the original C++ code. In C++, you exit the loop on EOF or when both of the numbers are 0. In Python, you exit only when both of the numbers are zero, failing with a runtime error on EOF. Additionally, in C++, cin >> kids >> cd will read kids and cd from standard input separated by whitespace, whereas your Python code reads it separated by newlines. Finally, you're using integer operations in C++, but floating-point calculations in Python.

Let's start with the EOF problem. To catch an EOF, you do a read as usual and catch the EOFError exception, e.g.:

try:
    kids = int(raw_input())
    cd   = int(raw_input())
except EOFError:
    break  # out of the loop we're in (not shown)

The floating-point problem is also pretty easy to solve: pow is not necessary; rather, Python's got an operator for it: **. Thus, you've got

print cd ** kids

Lastly, there's that pesky delimiter problem. How you solve this depends on how your input looks. If you've got two inputs per line, e.g.:

1 2
3 4
5 6

Then you'd want to read the line once, split it up, and convert each piece to an integer:

try:
    line = raw_input()
except EOFError:
    break
kids, cd = line.split()
kids = int(kids)
cd   = int(cd)

There are other solutions for other formats, including a direct parallel of the C++ code; but that's more complex and may not be necessary.

Lastly, consider using a while True loop without repeating the kids = ...; cd = ... code at the start and breaking when you want to stop, as you did in the C++ code.

Hugh Bothwell · Accepted Answer · 2014-01-31 03:59:50Z

1

while True:
    kids = int(raw_input())
    cd   = int(raw_input())
    if cd and kids:
        print(cd ** kids)
    else:
        break

Edit after looking at http://www.spoj.com/problems/UJ/ I would suggest

while True:
    n,d = [int(s) for s in raw_input().split()]
    if n and d:
        print(n ** d)
    else:
        break

edited Jan 31, 2014 at 3:59

answered Jan 31, 2014 at 3:45

Hugh Bothwell

57k9 gold badges91 silver badges103 bronze badges

3 Comments

user3213711 Over a year ago

Thank you, Hugh Bothwell. But your code still gives run time error for some reasons when I submitted it on the online judge SPOJ.

user3213711 Over a year ago

Here's the details: <br> number status signal time memory test 0 runtime error -1 0.03s 3740KB </br>

Hugh Bothwell Over a year ago

@user3213711: which SPOJ problem?

Collectives™ on Stack Overflow

Glitch in python code when converted from C++ code?

2 Answers 2

Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related