Search in Rotated Sorted Array

Suppose a sorted array 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.