EasyLeetCode #704Binary Search

Binary Search

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.

Constraints

1 <= nums.length <= 10^4, -10^4 < nums[i], target < 10^4, All integers in nums are unique, nums is sorted in ascending order

Examples

Input: nums = [-1,0,3,5,9,12], target = 9

Output: 4

Solution Approach

Divide search space in half repeatedly. Apply binary search on sorted arrays or search space. Check middle element and adjust bounds based on comparison.

Implementation

def search(nums, target):
    left, right = 0, len(nums) - 1
    while left <= right:
        mid = left + (right - left) // 2
        if nums[mid] == target:
            return mid
        elif nums[mid] < target:
            left = mid + 1
        else:
            right = mid - 1
    return -1

Complexity Analysis

Time Complexity

O(log n)

Space Complexity

O(1)

Key Learning Points

Divide search space by 2Only works on sorted dataPrevent integer overflow with mid calculation