Search in Rotated Sorted Array II问题及解法

问题描述：

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

).

Write a function to determine if a given target is in the array.

The array may contain duplicates.

问题分析：

对于查找一类问题，先考虑是否可以利用二分查找法。对于该题目，我们可以做一些适当的转化，使得查找可以遵循二分查找算法。

过程详见代码：

class Solution {
public:
bool search(vector<int>& nums, int target) {
if (nums.empty()) return false;
int left = 0;
int right = nums.size() - 1;
int mid;
while (left < right)
{
mid = left + (right - left) / 2;
if (nums[mid] == target) return true;
if (nums[mid] < nums[right])
{
if (nums[mid] < target && target <= nums[right]) left = mid + 1;
else right = mid;
}
else if (nums[mid] > nums[right])
{
if (nums[mid] > target && target >= nums[left]) right = mid;
else left = mid + 1;
}
else right--;
}
return nums[left] == target;
}
};