Problem Statement
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
Solution
class Solution:
def search(self, nums: List[int], target: int) -> int:
"""
0 1 2 3 4 5
----------------------
/ target
-1, 0, 3, 5, 9, 12
^a
^m
^b
"""
a, b = 0, len(nums) - 1
while a <= b:
m = (b + a) // 2
if nums[m] == target:
return m
elif nums[m] < target:
a = m + 1
else:
b = m - 1
return -1