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#704 Binary Search

Solved at: 2022-09-04

Question

Given an array of integers nums sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1.

You must write an algorithm with O(log n) runtime complexity.

Solution

class Solution:
def _search(self, nums: List[int], target:int, start:int, end:int) -> int:
mid = (end + start) // 2
# print(start, end, target, mid, nums[mid])
if nums[mid] == target:
return mid
elif nums[mid] != target and end <= start:
return -1
elif nums[mid] > target:
return self._search(nums, target, start, mid-1)
elif nums[mid] < target:
return self._search(nums, target, mid+1, end)
else:
return -1

def search(self, nums: List[int], target: int) -> int:
return self._search(nums, target, 0, len(nums)-1)

Results

Runtime

  • 542 ms, faster than 6.00% of Python3 online submissions for Binary Search.

Memory Usage

  • 15.5 MB, less than 73.17% of Python3 online submissions for Binary Search.

Complexity Analysis

Time

O(n)O(n)

Space

O(1)O(1)