Problem statement

https://binarysearch.com/problems/Equal-Piles/

Solution

Use counter and imagine we have 2, 7, 3, 4 frequencies of elements 1, 2, 3, 4. Then answer will be 2*0 + 7*1 + 3*2 + 4*3.

Complexity

It is O(n log n) for time and O(n) for space.

Code

class Solution:
    def solve(self, nums):
        cnt = sorted(list(Counter(nums).items()), key = lambda x: x[0])
        vals = [x for _, x in cnt]
        return sum(i*x for i, x in enumerate(vals))