704. Binary Search

Description

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.

Submitted Code

class Solution(object):
    def search(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        left = 0
        right = len(nums) - 1

        while left <= right:
            mid = (left + right) // 2

            if nums[mid] == target:
                return mid
            elif nums[mid] < target:
                left = mid + 1
            else:
                right = mid - 1
        
        return -1

Runtime: 0 ms | Beats 100.00%
Memory: 13.26 MB | Beats 93.13%

이미 오름차순으로 정렬되어 있기 때문에 이진 탐색 알고리즘으로 𝑂(log𝑛)의 시간 만에 빠르게 찾을 수 있다.