1409. Queries on a Permutation With Key

# Time:  O(nlogn)
# Space: O(n)

class BIT(object):  # Fenwick Tree, 1-indexed
    def __init__(self, n):
        self.__bit = [0] * n

    def add(self, i, val):
        while i < len(self.__bit):
            self.__bit[i] += val
            i += (i & -i)

    def sum(self, i):
        result = 0
        while i > 0:
            result += self.__bit[i]
            i -= (i & -i)
        return result


class Solution(object):
    def processQueries(self, queries, m):
        """
        :type queries: List[int]
        :type m: int
        :rtype: List[int]
        """
        bit = BIT(2*m+1)
        lookup = {}
        for i in xrange(1, m+1):
            bit.add(m+i, 1)
            lookup[i] = m+i
        result, curr = [], m
        for q in queries:
            i = lookup.pop(q)
            result.append(bit.sum(i-1))
            bit.add(i, -1)
            lookup[q] = curr
            bit.add(curr, 1)
            curr -= 1
        return result

Solution from kamyu104/LeetCode-Solutions · MIT