searchInRotatedArray.cpp

/*
Q. - There is an integer array nums sorted in ascending order (with distinct values).

Prior to being passed to your function, nums is possibly rotated at an unknown pivot index k (1 <= k < nums.length) such that the resulting array is [nums[k], nums[k+1], ..., nums[n-1], nums[0], nums[1], ..., nums[k-1]] (0-indexed). For example, [0,1,2,4,5,6,7] might be rotated at pivot index 3 and become [4,5,6,7,0,1,2].

Given the array nums after the possible rotation and an integer target, return the index of target if it is in nums, or -1 if it is not in nums.

You must write an algorithm with O(log n) runtime complexity.
*/

Solution - straightforward binary search

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