Commit acb77c1

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Amogh Singhal

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Create merge_sort.py

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	`1`	`+def merge_sort(array, left, right):`
	`2`	`+ # derive the mid-point`
	`3`	`+ if left < right:`
	`4`	`+ mid = (left+(right-1))//2`
	`5`	`+ # print("mid", mid)`
	`6`	`+`
	`7`	`+ # sort the first and second halves`
	`8`	`+ merge_sort(array, left, mid)`
	`9`	`+ merge_sort(array, mid+1, right)`
	`10`	`+ # merge back`
	`11`	`+ merge(array, left, mid, right)`
	`12`	`+`
	`13`	`+def merge(array, left, mid, right):`
	`14`	`+ # initialize sizes for the sub-arrays`
	`15`	`+ size_left = mid - left + 1`
	`16`	`+ # print("size_left", size_left)`
	`17`	`+ size_right = right - mid`
	`18`	`+ # print("size_right", size_right)`
	`19`	`+`
	`20`	`+ # create the temp sub-arrays`
	`21`	`+ LEFT = [0] * (size_left)`
	`22`	`+ # print("LEFT", LEFT)`
	`23`	`+ RIGHT = [0] * (size_right)`
	`24`	`+ # print("RIGHT", RIGHT)`
	`25`	`+`
	`26`	`+ # copy data to the sub-arrays`
	`27`	`+ for i in range(0, size_left):`
	`28`	`+ LEFT[i] = array[left + i]`
	`29`	`+`
	`30`	`+ for j in range(0, size_right):`
	`31`	`+ RIGHT[j] = array[mid + 1 + j]`
	`32`	`+`
	`33`	`+ # merge into original array`
	`34`	`+ i, j, k = 0, 0, 1`
	`35`	`+`
	`36`	`+ while i < size_left and j < size_right:`
	`37`	`+ if LEFT[i] <= RIGHT[j]:`
	`38`	`+ array[k] = LEFT[i]`
	`39`	`+ i += 1`
	`40`	`+ else:`
	`41`	`+ array[k] = RIGHT[j]`
	`42`	`+ j += 1`
	`43`	`+ k += 1`
	`44`	`+`
	`45`	`+arr = [6, 5, 3, 1, 8, 7, 2, 4]`
	`46`	`+merge_sort(arr, 0, len(arr))`

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