Search in Rotated Sorted Array

Question

## Problem

Search a target in an ascending array rotated at an unknown pivot; O(log n).

## Example
```
[4,5,6,7,0,1,2], target=0 -> 4
```

## Constraints
- 1 ≤ n ≤ 5000

## Approach
Modified binary search deciding which half is sorted each step.