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

Time complexity : O(log(n))
Space complexity : O(1)

class Solution {
public:
    int search(vector<int>& nums, int target) {
        int l=0, r=nums.size()-1;
        while (l < r) {
            int m=(l+r)>>1;
            printf("%d, %d, %d\n", l, m, r);
            if (nums[m] < target)
                l = m + 1;
            else
                r = m;
        }
        return nums[l] == target ? l : -1;
    }
};