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sort in python
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#The merge method takes in the two subarrays and creates a output array | |
def merge(left, right): | |
result = [] | |
i , j = 0 , 0 | |
while i < len (left) and j < len (right): # iterate through both arrays and arrange the elements in sorted order | |
if left[i] <= right [j]: | |
result.append(left[i]) | |
i+=1 | |
else: | |
result.append(right[j]) | |
j+=1 | |
#The loop may break before all elements are copied hence append the remaining elements | |
result += left[i:] | |
result += right[j:] | |
return result | |
#The mergesort method to split the arrays into smaller subarrays | |
def mergesort(lst): | |
if len(lst) <= 1: | |
return lst | |
middle = int(len(lst) / 2) | |
left = mergesort(lst[:middle]) | |
right = mergesort(lst[middle:]) | |
return merge(left, right) | |
if __name__ == '__main__': | |
print mergesort([3, 4, 8, 0, 6, 7, 4, 2, 1, 9, 4, 5]) |
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def sort(array=[12,4,5,6,7,3,1,15]): | |
less = [] | |
equal = [] | |
greater = [] | |
if len(array) > 1: | |
pivot = array[0] | |
for x in array: | |
if x < pivot: | |
less.append(x) | |
if x == pivot: | |
equal.append(x) | |
if x > pivot: | |
greater.append(x) | |
# Don't forget to return something! | |
return sort(less)+equal+sort(greater) # Just use the + operator to join lists | |
# Note that you want equal ^^^^^ not pivot | |
else: # You need to hande the part at the end of the recursion - when you only have one element in your array, just return the array. | |
return array |
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def partition(array, begin, end): | |
pivot = begin | |
for i in xrange(begin+1, end+1): | |
if array[i] <= array[begin]: | |
pivot += 1 | |
array[i], array[pivot] = array[pivot], array[i] | |
array[pivot], array[begin] = array[begin], array[pivot] | |
return pivot | |
def quicksort(array, begin=0, end=None): | |
if end is None: | |
end = len(array) - 1 | |
def _quicksort(array, begin, end): | |
if begin >= end: | |
return | |
pivot = partition(array, begin, end) | |
_quicksort(array, begin, pivot-1) | |
_quicksort(array, pivot+1, end) | |
return _quicksort(array, begin, end) |
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