문제 : ZeroPage:PrimaryArithmetic

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[Recursion]을 이용해보기.  
{{{#!python
import unittest

def countCarry(a,b, carry=0):
    if a+b==0:
        return 0
    carry = (a%10+b%10+carry) / 10
    return carry + countCarry(a/10, b/10, carry)

def countCarryWithTp(a,b, tcarry=0, pcarry=0):
    if a+b==0:
        return tcarry
    pcarry = (a%10+b%10+pcarry) / 10
    tcarry += pcarry
    return countCarryWithTp(a/10, b/10, tcarry, pcarry)

class SomeTest(unittest.TestCase):
    def testCountCarry(self):
        self.assertEquals(3, countCarry(1,999))
        self.assertEquals(1, countCarry(1,889))
        self.assertEquals(2, countCarry(555,345))
    def testCountCarry(self):
        self.assertEquals(3, countCarryWithTp(1,999))
        self.assertEquals(1, countCarryWithTp(1,889))
        self.assertEquals(2, countCarryWithTp(555,345))

if __name__=='__main__':
    unittest.main()
}}}
countCarryWithTp와 같은 형태는 쉽게 나왔으나, countCarry와 같은 형태는 바로 유추되지 않았다. 어떠한 발상의 전환이 필요한 것일까. -- [[yong27]] <<DateTime(2006-02-27T10:18:33Z)>>