# Time:  O(logn)
# Space: O(1)

# Given a sorted (in ascending order) integer array nums of n elements
# and a target value, write a function to search target in nums.
# If target exists, then return its index, otherwise return -1.
#
# 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
#
# Note:
# - You may assume that all elements in nums are unique.
# - n will be in the range [1, 10000].
# - The value of each element in nums will be in the range [-9999, 9999].


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

Create binary-search.py