Leetcode: 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.

这样的题，小于O(n)才有意义。

class Solution {
public:
    int search(int A[], int n, int target) {
        int low = 0;
        int up = n - 1;
        int mid;
        while (low <= up) {
            mid = low + (up - low) / 2;
            if (A[mid] == target) {
                return mid;
            }
            else if (A[mid] >= A[low]) {
                // left part is sorted
                if (A[mid] > target && A[low] <= target) {
                    up = mid - 1;
                }
                else {
                    low = mid + 1;
                }
            }
            else {
                // right part is sorted
                if (A[mid] < target && A[up] >= target) {
                    low = mid + 1;
                }
                else {
                    up = mid - 1;
                }
            }
        }
        
        return -1;
    }
};