LeetCode 704. Binary Search

Problem :

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 :

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

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.

Solution :

class Solution:
    def search(self, nums: List[int], target: int) -> int:
        idx = 0
        max_ = len(nums)-1
        min_ = 0
        while (nums[idx] != target):
            if (max_-min_)<=1:
                if (nums[max_]==target):
                    idx=max_
                elif (nums[min_]==target):
                    idx=min_
                else :
                    idx=-1
                break
            else :
                idx = (max_+min_)//2
                if nums[idx] > target: max_=idx
                else : min_=idx
        return idx

An official solution from LeetCode

class Solution:
    def search(self, nums: List[int], target: int) -> int:
        left, right = 0, len(nums) - 1
        while left <= right:
            pivot = left + (right - left) // 2
            if nums[pivot] == target:
                return pivot
            if target < nums[pivot]:
                right = pivot - 1
            else:
                left = pivot + 1
        return -1

Link to the Source :

https://leetcode.com/problems/binary-search/