CODEWITHSUNDEEP
pythonsortingrecursionquicksort
TimeseriesAnalysis
TimeseriesAnalysis

Reputation: 11

Why does this implementation of QuickSort not work?

I tried to translate the Quicksort code from Java to Python but it didnt work. Can someone tell me where the Problem is? I'm getting a "maximum recursion depth exceeded in comparison" but with my example I only want to order less than 10 integers so I dont think this is the real problem...

def help(array, low, high):
    pivot = array[low]
    fromhigh = high
    fromlow = low
    while True:
        while(array[fromhigh]>pivot):
            fromhigh = fromhigh-1
        while(array[fromlow]<pivot):
            fromlow = fromlow+1
        if(fromlow<fromhigh):
            array[fromlow], array[fromhigh] = array[fromhigh], array[fromlow]
        else:
            return fromhigh


def quickSort(array, low, high):
   if (low<=high):
       pivot = help(array, low, high)
       quickSort(array, low, pivot)
       quickSort(array, pivot + 1, high)


#Testarray
array = [10, 7, 2 , 8, 9, 1, 5, 11, 13]
n = len(array)
quickSort(array, 0, n-1)
print("Sorted Array:")
for i in range(n):
    print("%d" % array[i]),

Upvotes: 1

Views: 36

Answers (1)

ikicic
ikicic

Reputation: 98

If you add a print(low, high) at the beginning of your quickSort function, you'll notice that it prints 0 0 all the time until it crashes.

The if condition there is incorrect. Instead of low <= high it should be low < high, because you don't want to continue sorting a single-element subarray.

Upvotes: 1

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