假设按照升序排序的数组在预先未知的某个点上进行了旋转。
( 例如,数组 [0,1,2,4,5,6,7] 可能变为 [4,5,6,7,0,1,2] )。
搜索一个给定的目标值,如果数组中存在这个目标值,则返回它的索引,否则返回 -1 。
你可以假设数组中不存在重复的元素。
你的算法时间复杂度必须是 O(log n) 级别。
示例 1:
输入: nums = [4,5,6,7,0,1,2], target = 0
输出: 4
示例 2:
输入: nums = [4,5,6,7,0,1,2], target = 3
输出: -1
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/search-in-rotated-sorted-array
著作权归领扣网络所有。商业转载请联系官方授权,非商业转载请注明出处。
class Solution {
public int search(int[] nums, int target) {
if(nums.length == 0) return -1;
int n = searchtarget(nums, target, 0, nums.length-1);
return (nums[n]==target)?n:-1;
}
public int searchtarget(int[] nums, int target, int low, int high) {
int mid = (low+high)/2;
if(nums[high] < nums[low]){
return searchtarget(nums, target, low, mid)+searchtarget(nums, target, mid+1, high);
}
else {
while(low <= high) {
mid = (low+high)/2;
if(target > nums[high]) return 0;
if(target < nums[low]) return 0;
if(target == nums[mid]) return mid;
else if(target < nums[mid]) high = mid-1;
else low = mid+1;
}
}
return -1;
}
}