- Difficulty: Medium
- Tags: LeetCode, Medium, Array, Hash Table, Binary Search, Dynamic Programming, Sorting, leetcode-2501, O(nlogn), O(n), DP
Problem
You are given an integer array nums
. A subsequence of nums
is called a square streak if:
- The length of the subsequence is at least
2
, and - after sorting the subsequence, each element (except the first element) is the square of the previous number.
Return the length of the longest square streak in nums
, or return -1
if there is no square streak.
A subsequence is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.
Example 1:
Input: nums = [4,3,6,16,8,2] Output: 3 Explanation: Choose the subsequence [4,16,2]. After sorting it, it becomes [2,4,16]. - 4 = 2 * 2. - 16 = 4 * 4. Therefore, [4,16,2] is a square streak. It can be shown that every subsequence of length 4 is not a square streak.
Example 2:
Input: nums = [2,3,5,6,7] Output: -1 Explanation: There is no square streak in nums so return -1.
Constraints:
2 <= nums.length <= 105
2 <= nums[i] <= 105