SearchSortedRotatedArray.java

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

// eg Input: arr = [4,5,6,7,0,1,2], target = 0, Output: 4 



class SearchRotatedSortedArray {
    public int search(int[] arr, int target) {
        int pivot = findPivot(arr);
        if (pivot == -1) {
            return binarySearch(arr, target, 0, arr.length - 1);
        }
        if (arr[pivot] == target) {
            return pivot;
        } else if (target >= arr[0]) {
            return binarySearch(arr, target, 0, pivot - 1);
        }
        return binarySearch(arr, target, pivot + 1, arr.length - 1);
    }

    int binarySearch(int[] arr, int target, int start, int end) {
        while (start <= end) {
            int mid = start + (end - start) / 2;
            if (arr[mid] == target) {
                return mid;
            } else if (arr[mid] > target) {
                end = mid - 1;
            } else {
                start = mid + 1;
            }
        }
        return -1;
    }

    int findPivot(int[] nums) {
        int start = 0;
        int end = nums.length - 1;
        while (start <= end) {
            int mid = start + (end - start) / 2;
            if (mid < end && nums[mid] > nums[mid + 1]) {
                return mid;
            }
            if (mid > start && nums[mid] < nums[mid - 1]) {
                return mid - 1;
            }
            if (nums[mid] < nums[start]) {
                end = mid - 1;
            } else {
                start = mid + 1;
            }
        }
        return -1;
    }
}