Skip to content

Link to Question

MEDIUM

Search in Rotated Sorted Array

There is an integer array nums sorted in ascending order (with distinct values), which is rotated at an unknown pivot index k (0 <= k < nums.length) such that the resulting array is [nums[k], nums[k+1], ..., nums[n-1], nums[0], nums[1], ..., nums[k-1]] (0-indexed).

Given the array nums after the rotation and an integer target, return the index of target if it is in nums, or -1 if it is not in nums.

You must write an algorithm with O(log n) runtime complexity.

Example

Input:

nums = [4,5,6,7,0,1,2], target = 0

Output:

4

Explanation:
0 is at index 4 in the rotated array.

Constraints

  • 1 ≤ nums.length ≤ 5000
  • -10⁴ ≤ nums[i] ≤ 10⁴
  • All values of nums are unique.
  • nums is guaranteed to be rotated at some pivot.
  • -10⁴ ≤ target ≤ 10⁴
  • Time Complexity: O(log n)
  • Space Complexity: O(1)
C++
class Solution {
public:
    int search(vector<int>& nums, int target) {
        int l = 0, r = nums.size() - 1;
        while (l <= r) {
            int m = l + (r - l) / 2;
            if (nums[m] == target) return m;
            if (nums[l] <= nums[m]) {
                if (nums[l] <= target && target < nums[m]) r = m - 1;
                else l = m + 1;
            } else {
                if (nums[m] < target && target <= nums[r]) l = m + 1;
                else r = m - 1;
            }
        }
        return -1;
    }
};