Title
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]).
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.
Your algorithm’s runtime complexity must be in the order of O(log n).
Example 1:
Input: nums = [4,5,6,7,0,1,2], target = 0
Output: 4
Example 2:
Input: nums = [4,5,6,7,0,1,2], target = 3
Output: -1
轮转数组查找
Solution
//cpp:
class Solution {
public:
int search(vector<int>& nums, int target) {
int n = nums.size();
int lo = 0, hi = n - 1;
while (lo <= hi) {
int mid = lo + (hi - lo) / 2;
if (nums[mid] == target) {
return mid;
}
else if (nums[lo] <= nums[mid]) {
if (nums[lo] <= target && target < nums[mid]) {
hi = mid - 1;
}
else {
lo = mid + 1;
}
}
else {
if (nums[mid] < target&&target <= nums[hi]) {
lo = mid + 1;
}
else {
hi = mid - 1;
}
}
}
return -1;
}
};