Problem:
Suppose an array sorted in ascending order 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.
Your algorithm's runtime complexity must be in the order of O(log n).
Example 1:
Input: nums = [4,5,6,7,0,1,2], target = 0
Output: 4
Example 2:
Input: nums = [4,5,6,7,0,1,2], target = 3
Output: -1
思路：
Solution (C++):
int search(vector<int>& nums, int target) {
if (nums.empty()) return -1;
int n = nums.size();
int pivot = n - 1;
for (int i = 0; i < n - 1; ++i) {
if (nums[i] > nums[i+1]) { pivot = i; break; }
}
int index = binarySearch(nums, 0, pivot, target);
if (index == -1) index = binarySearch(nums, pivot+1, n-1, target);
return index;
}
int binarySearch(vector<int>& v, int low, int high, int target) {
while (low <= high) {
int mid = low + (high - low) / 2;
if (v[mid] == target) return mid;
else if (v[mid] < target) low = mid + 1;
else high = mid - 1;
}
return -1;
}
性能：
Runtime: 0 ms Memory Usage: 6.6 MB
思路：
Solution (C++):
性能：
Runtime: ms Memory Usage: MB
