Search in Rotated Sorted Array

Problem:

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.

Solution:

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