# 2938. Separate Black and White Balls """ there are 'n' balls on a table, each ball has a colour black or white. you are given a 0-indexed binary string 's' of length 'n', where 1 and 0 represent black and white balls respectively. in each step, you can choose two adjacent balls and swap them. return the minimum number of steps to group all the black balls to the right and all the white balls to the left """ class Solution(object): def minimumSteps(self, s): """ :type s: str :rtype: int """ one_cnt, swap_cnt = 0, 0 for i in range(len(s) - 1, -1, -1): if s[i] == "1": swap_cnt += one_cnt else: one_cnt += 1 return swap_cnt if __name__ == "__main__": obj = Solution() print(obj.minimumSteps("101")) print(obj.minimumSteps("100"))