7. Binary Search

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 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

Note:

1. You may assume that all elements in nums are unique.
2. n will be in the range [1, 10000].
3. The value of each element in nums will be in the range [-9999, 9999].

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) {
 high = mid-1;
 } else {
 low = mid+1;
 }
 }
 
 return -1;
 
 }
}