LeetCode #33 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.

class Solution {
private:
int find_rotate_index(vector<int>& nums) {
int left = 0, right = nums.size() - 1;
while(left < right){
int mid = (left + right) >> 1;
if(nums[mid] > nums[right])  left = mid + 1;
else right = mid;
}
return left;
}

public:
int search(vector<int>& nums, int target) {
int rotate_index = find_rotate_index(nums);
int left, right, last_index = nums.size() - 1;
if(target > nums[last_index]) {left = 0; right = rotate_index - 1;}
else if(target < nums[last_index]) {left = rotate_index; right = last_index - 1;}
else return last_index;

while(left <= right){
int mid = (left + right) >> 1;
if(nums[mid] < target) left = mid + 1;
else if(nums[mid] > target) right = mid - 1;
else return mid;
}
return -1;
}
};