704. Binary Search

Easy

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.

解題

Binary search

func search(nums []int, target int) int {
    left := 0
    right := len(nums)-1

    for left <= right {
        mid := ( left + right )/2

        if nums[mid] == target { return mid }

        if nums[mid] > target { 
            right = mid - 1
        } else {
            left = mid + 1
        }
    }

    return -1
}