704. 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.

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

Example 2:

Input: nums = [-1,0,3,5,9,12], target = 2
Output: -1
Explanation: 2 does not exist in nums so return -1

Solution :

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

Link : https://leetcode.com/problems/binary-search/?envType=study-plan&id=algorithm-i