Binary Search (LeetCode)

 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

Solution(Java)

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