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Algorithm

704. Binary Search

Description

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.

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
  • -9999 <= nums[i], target <= 9999
  • All the integers in nums are unique.
  • nums is sorted in an ascending order.

Solution

class Solution {
    public int search(int[] nums, int target) {
        int low = 0;
        int high = nums.length-1;
        while(low<=high){
            int mid = (low+high)/2;
            if(nums[mid] == target){
                return mid;
            }else if(nums[mid] < target){
                low = mid+1;
            }else{
                high = mid-1;
            }
        }
        return -1;
    }
}

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