2586 Longest Square Streak In An Array

Longest Square Streak in an Array

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

class Solution:
    def longestSquareStreak(self, nums: List[int]) -> int:
        nums.sort()
        res = []
        mp = {}
        for k in nums:
            s = int(math.sqrt(k))
            print(s,math.sqrt(k), s == math.sqrt(k) )
            if s in mp and s == math.sqrt(k):
                mp[k] = (mp[s] + 1)
                res.append(mp[k])
                
            else:
                mp[k] = 0
        #print(res, mp)
        return max(res) +  1 if len(res) > 0 else -1