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53 lines
2.2 KiB
53 lines
2.2 KiB
"""
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File: binary_search.py
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Created Time: 2022-11-26
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Author: timi (xisunyy@163.com)
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"""
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def binary_search(nums: list[int], target: int) -> int:
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"""Binary search (double closed interval)"""
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# Initialize double closed interval [0, n-1], i.e., i, j point to the first element and last element of the array respectively
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i, j = 0, len(nums) - 1
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# Loop until the search interval is empty (when i > j, it is empty)
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while i <= j:
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# Theoretically, Python's numbers can be infinitely large (depending on memory size), so there is no need to consider large number overflow
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m = i + (j - i) // 2 # Calculate midpoint index m
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if nums[m] < target:
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i = m + 1 # This situation indicates that target is in the interval [m+1, j]
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elif nums[m] > target:
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j = m - 1 # This situation indicates that target is in the interval [i, m-1]
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else:
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return m # Found the target element, thus return its index
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return -1 # Did not find the target element, thus return -1
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def binary_search_lcro(nums: list[int], target: int) -> int:
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"""Binary search (left closed right open interval)"""
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# Initialize left closed right open interval [0, n), i.e., i, j point to the first element and the last element +1 of the array respectively
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i, j = 0, len(nums)
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# Loop until the search interval is empty (when i = j, it is empty)
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while i < j:
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m = i + (j - i) // 2 # Calculate midpoint index m
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if nums[m] < target:
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i = m + 1 # This situation indicates that target is in the interval [m+1, j)
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elif nums[m] > target:
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j = m # This situation indicates that target is in the interval [i, m)
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else:
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return m # Found the target element, thus return its index
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return -1 # Did not find the target element, thus return -1
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"""Driver Code"""
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if __name__ == "__main__":
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target = 6
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nums = [1, 3, 6, 8, 12, 15, 23, 26, 31, 35]
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# Binary search (double closed interval)
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index = binary_search(nums, target)
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print("Index of target element 6 =", index)
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# Binary search (left closed right open interval)
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index = binary_search_lcro(nums, target)
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print("Index of target element 6 =", index)
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