where the function has problem? n = 900 is OK , but n = 1000 is ERROR

jc chenjii at gmail.com
Mon Aug 1 11:11:16 CEST 2011


# Get Fibonacci Value
#    Fibonacci(N) = Fibonacci(N-1) + Fibonacci(N-2)
#
# n = 900 is OK
# n = 1000 is ERROR , Why
#
# What Wrong?
#

cache = []

def fibo( n ):
    
    try:    
        if cache[n] != -1:
            return cache[n]
        else:
            if 0 == n:
                r = 0
            elif 1 == n:
                r = 1
            else:
                r = fibo(n-1) + fibo(n-2)

            cache[n] = r
            return r
    except:
        print "EXCEPT: " + str(n)
        

if __name__ == '__main__':

# This n = 900 is OK
# But n = 1000 is ERROR

    n = 900
    cache = range(0 , n + 1 , 1)

    for i in cache:
        cache[i] = -1
    
    print "Fibo(" + str(n) + ") = " + str(fibo(n))
    print "\n"
    print "\n"
        



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