LeetCode-Binary Search

Given an array of integers nums which is 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.

Example 1:

Input: nums = [-1,0,3,5,9,12], target = 9
Output: 4
Explanation: 9 exists in nums and its index is 4

Example 2:

Input: nums = [-1,0,3,5,9,12], target = 2
Output: -1
Explanation: 2 does not exist in nums so return -1

Constraints:

• 1 <= nums.length <= 104
• -104 < nums[i], target < 104
• All the integers in nums are unique.
• nums is sorted in ascending order.

SourceCode

class Solution:

def search(self, nums: List[int], target: int) -> int:

low = 0

high = len(nums)

if high > 0:

while high >= low:

mid = (high + low) // 2

if mid <= high and mid < len(nums):

if nums[mid] == target:

return mid

elif nums[mid] > target:

high = mid — 1

else:

low = mid + 1

else:

return -1

return -1

else:

return -1