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search-for-range.py
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search-for-range.py
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# SEARCH FOR RANGE
# O(N) time and space
def searchForRange(array, target):
# Write your code here.
positions = [-1, -1]
binarySearch(array, target, 0, len(array) - 1, positions)
return positions
def binarySearch(array, target, left, right, positions):
if left > right:
return
mid = (left + right) // 2
if array[mid] != target:
if array[mid] < target:
binarySearch(array, target, mid + 1, right, positions)
else:
binarySearch(array, target, left, mid - 1, positions)
else:
if mid == 0 or array[mid-1] != target:
positions[0] = mid
if mid == len(array) - 1 or array[mid+1] != target:
positions[1] = mid
if -1 not in positions:
return
binarySearch(array, target, mid + 1, right, positions)
binarySearch(array, target, left, mid - 1, positions)
# O(logN) time and space
def searchForRange(array, target):
# Write your code here.
positions = [-1, -1]
binarySearch(array, target, 0, len(array) - 1, positions, True)
binarySearch(array, target, 0, len(array) - 1, positions, False)
return positions
def binarySearch(array, target, left, right, positions, goLeft):
if left > right:
return
mid = (left + right) // 2
if array[mid] != target:
if array[mid] < target:
binarySearch(array, target, mid + 1, right, positions, goLeft)
else:
binarySearch(array, target, left, mid - 1, positions, goLeft)
else:
if goLeft:
if mid == 0 or array[mid-1] != target:
positions[0] = mid
else:
binarySearch(array, target, left, mid - 1, positions, goLeft)
else:
if mid == len(array) - 1 or array[mid+1] != target:
positions[1] = mid
else:
binarySearch(array, target, mid + 1, right, positions, goLeft)
# O(logN) time and O(1) space
def searchForRange(array, target):
# Write your code here.
positions = [-1, -1]
binarySearch(array, target, 0, len(array) - 1, positions, True)
binarySearch(array, target, 0, len(array) - 1, positions, False)
return positions
def binarySearch(array, target, left, right, positions, goLeft):
while left <= right:
mid = (left + right) // 2
if array[mid] != target:
if array[mid] < target:
left = mid + 1
else:
right = mid - 1
else:
if goLeft:
if mid == 0 or array[mid-1] != target:
positions[0] = mid
break
else:
right = mid - 1
else:
if mid == len(array) - 1 or array[mid+1] != target:
positions[1] = mid
break
else:
left = mid + 1