704. Binary Search

https://leetcode.com/problems/binary-search/?envType=study-plan&id=algorithm-i

# target 을 nums 에서 찾는 문제
# 존재하면 return index, 없으면 -1 

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

#         left = nums[:len(nums)//2] # nums[0:3] -1,0,3
#         right = nums[len(nums)//2:] # nums[3:] 5,9,12
    
#         if target in left : 
#             for idx, i in enumerate(left) :
#                 if target == i :
#                     return idx

#         if target in right : 
#             for idx, j in enumerate(right):
#                 if target == j :
#                     return idx + len(left)
        
#         else : 
#             return -1


class Solution:
    def search(self, nums: List[int], target: int) -> int:
        left = 0
        right = len(nums)-1 # 5

        while left<=right :
            middle = (left+right)//2  # 3
            if nums[middle] == target :
                return middle
            elif nums[middle] < target :
                left = middle + 1 
            elif nums[middle] > target :
                right = middle - 1

        return -1