704. Binary Search - Easy
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 innums
and its index is 4
Example 2:
Input:nums
= [-1,0,3,5,9,12],target
= 2 Output: -1 Explanation: 2 does not exist innums
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]
.
classical binary search
time: O(logn), space: O(1)
class Solution { public int search(int[] nums, int target) { if(nums == null || nums.length == 0) { return -1; } int left = 0, right = nums.length - 1; while(left <= right) { int mid = left + (right - left) / 2; if(nums[mid] == target) { return mid; } else if(nums[mid] < target) { left = mid + 1; } else { right = mid - 1; } } return -1; } }