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Commit 225ec0e

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added quicksort and binary search
1 parent fb354d1 commit 225ec0e

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‎Utils/sort.py‎

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Original file line numberDiff line numberDiff line change
@@ -85,9 +85,70 @@ def merge(arr, left, mid, right):
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# quick sort
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def quickSort(arr):
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def partition(arr, left, right):
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pivotIndex = left
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pivot = arr[right]
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print("working on index {} to {}:".format(left, right))
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for i in range(left, right):
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print("i={}: comparing {} and {}".format(i, arr[i], pivot))
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if arr[i] <= pivot:
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arr[pivotIndex], arr[i] = arr[i], arr[pivotIndex]
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pivotIndex += 1
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print("{}, pivotIndex={}".format(arr, pivotIndex))
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arr[pivotIndex], arr[right] = arr[right], arr[pivotIndex]
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return pivotIndex
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def sort(arr, left, right):
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if left < right:
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pivotIndex = partition(arr, left, right)
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sort(arr, left, pivotIndex-1)
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sort(arr, pivotIndex+1, right)
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sort(arr, 0, len(arr)-1)
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# binary search (recursive)
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def binarySearch_rec(arr, target, left=0, right=None):
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if right is None:
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right = len(arr)-1
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if left > right:
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return -1
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mid = (left+right)//2
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if arr[mid] == target:
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print("{} == {}".format(arr[mid], target))
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return mid
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elif arr[mid] > target:
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print("{} > {}. will now search in {}".format(
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arr[mid], target, arr[left:mid]))
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return binarySearch_rec(arr, target, left, mid-1)
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else:
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print("{} < {}. will now search in {}".format(
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arr[mid], target, arr[mid+1:right+1]))
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return binarySearch_rec(arr, target, mid+1, right)
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# binary search (iterative)
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def binarySearch_iter(arr, target):
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left = 0
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right = len(arr)-1
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while left < right:
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mid = (left+right) // 2
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if arr[mid] == target:
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print("{} == {}".format(arr[mid], target))
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return mid
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elif arr[mid] > target:
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print("{} > {}. will now search in {}".format(
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arr[mid], target, arr[left:mid]))
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right = mid
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else:
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print("{} < {}. will now search in {}".format(
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arr[mid], target, arr[mid+1:right+1]))
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left = mid+1
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return -1
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if __name__ == "__main__":
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# generate random array
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arr = list()
@@ -127,3 +188,32 @@ def merge(arr, left, mid, right):
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arr_copy = list(arr)
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mergeSort(arr_copy)
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print("Sorted:", arr_copy)
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# quick sort test
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print()
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print("*** Quick Sort ***")
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print("Original Array:", arr)
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arr_copy = list(arr)
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quickSort(arr_copy)
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print("Sorted:", arr_copy)
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# binary search test
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print()
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print("*** Binary Search (Recursive) ***")
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target = 32
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print("Sorted Array: {}, target = {}".format(arr_copy, target))
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index = binarySearch_rec(arr_copy, target)
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if index > 0:
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print("Index of {} = {}".format(target, index))
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else:
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print("{} not found in array".format(target))
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print()
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print("*** Binary Search (Iterative) ***")
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target = 97
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print("Sorted Array: {}, target = {}".format(arr_copy, target))
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index = binarySearch_iter(arr_copy, target)
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if index > 0:
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print("Index of {} = {}".format(target, index))
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else:
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print("{} not found in array".format(target))

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