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find_element_range_sorted_array.py
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58 lines (42 loc) · 1.25 KB
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'''
Find First and Last Position of Element in Sorted Array
Given an array of integers nums sorted in ascending order,
find the starting and ending position of a given target value.
If the target is not found in the array, return [-1, -1].
Input: [5, 7, 7, 8, 8, 10], 8
Output: [3, 4]
Input: [5, 7, 7, 8, 8, 10], 6
Output: [-1, -1]
=========================================
Use binary search twice to find the range.
Time Complexity: O(LogN)
Space Complexity: O(1)
'''
############
# Solution #
############
def search_range(nums, target):
left_idx = binary_search(nums, target, True)
if (left_idx == len(nums)) or (nums[left_idx] != target):
return [-1, -1]
right_idx = binary_search(nums, target, False) - 1
return [left_idx, right_idx]
def binary_search(nums, target, equal=True):
left = 0
right = len(nums)
while left < right:
mid = (left + right) // 2
if (nums[mid] > target) or (equal and nums[mid] == target):
right = mid
else:
left = mid + 1
return left
###########
# Testing #
###########
# Test 1
# Correct result => [3, 4]
print(search_range([5, 7, 7, 8, 8, 10], 8))
# Test 2
# Correct result => [-1, -1]
print(search_range([5, 7, 7, 8, 8, 10], 6))