day-19.cpp

/*
Question: Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.

(i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]).

You are given a target value to search. If found in the array return its index, otherwise return -1.

You may assume no duplicate exists in the array.

Your algorithm's runtime complexity must be in the order of O(log n).

Example 1:

Input: nums = [4,5,6,7,0,1,2], target = 0
Output: 4
Example 2:

Input: nums = [4,5,6,7,0,1,2], target = 3
Output: -1
*/

// O(logN) solution
class Solution {
   public:
    int binarySearch(vector<int> nums, int low, int high, int target) {
        while (low <= high) {
            int mid = low + ((high - low) / 2);
            if (nums[mid] == target)
                return mid;
            else if (nums[mid] < target)
                low = mid + 1;
            else
                high = mid - 1;
        }

        return -1;
    }

    int search(vector<int>& nums, int target) {
        if (nums.size() == 0) return -1;
        int low = 0;
        int high = nums.size() - 1;

        while (low < high) {
            int mid = low + (high - low) / 2;
            if (nums[mid] > nums[high]) {
                low = mid + 1;
            } else {
                high = mid;
            }
        }

        int pivot = low;
        low = 0;
        high = nums.size() - 1;
        int ans;
        if (target >= nums[pivot] && target <= nums[high]) {
            low = pivot;
        } else {
            high = pivot;
        }
        return binarySearch(nums, low, high, target);
    }
};