Leetcode 33. Search in Rotated Sorted Array (Hard) (cpp)

/*
33. Search in Rotated Sorted Array (Hard)

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.
*/
class Solution {
public:
int search(vector<int>& nums, int target) {
int first = 0, last = nums.size() - 1;
while (first != last) {
int mid = first + (last - first) / 2;
//分半
if (nums[mid] == target) {
return mid;
}
else if (nums[first] <= nums[mid]) {
if (nums[first] <= target && target < nums[mid]) {
last = mid;
}
else {
first = mid + 1;
}
}
else {
if (nums[mid] < target && target <= nums[last]) {
first = mid + 1;
}
else {
last = mid;
}
}
}
if (nums[first] == target) {
return first;
}
return -1;
}
};