1. 二分查找
通过左和中的大小关系判断是升序还是中间旋转了。
时间O(logn)，空间O(1)。
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| class Solution {
public:
int search(vector<int>& nums, int target) {
int n = nums.size();
if (n == 0)
return -1;
int ans = -1;
int left = 0, right = n - 1;
while (left <= right) {
int mid = (left + right) / 2;
if (nums[left] > target) {
if (nums[mid] >= nums[left])
left = mid + 1;
else {
if (nums[mid] > target)
right = mid - 1;
else if (nums[mid] < target)
left = mid + 1;
else {
ans = mid;
break;
}
}
} else if (nums[left] < target) {
if (nums[mid] >= nums[left]) {
if (nums[mid] > target)
right = mid - 1;
else if (nums[mid] < target)
left = mid + 1;
else {
ans = mid;
break;
}
} else
right = mid - 1;
} else {
ans = left;
break;
}
}
return ans;
}
};
|