find-anagram-mappings.py

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

# Given two lists Aand B, and B is an anagram of A.
# B is an anagram of A means B is made by randomizing the order of the elements in A.
#
# We want to find an index mapping P, from A to B. A mapping P[i] = j
# means the ith element in A appears in B at index j.
#
# These lists A and B may contain duplicates. If there are multiple answers, output any of them.
#
# For example, given
# A = [12, 28, 46, 32, 50]
# B = [50, 12, 32, 46, 28]
#
# We should return
# [1, 4, 3, 2, 0]
# as P[0] = 1 because the 0th element of A appears at B[1], and P[1] = 4
# because the 1st element of A appears at B[4], and so on.
#
# Note:
# - A, B have equal lengths in range [1, 100].
# - A[i], B[i] are integers in range [0, 10^5].

import collections


class Solution(object):
    def anagramMappings(self, A, B):
        """
        :type A: List[int]
        :type B: List[int]
        :rtype: List[int]
        """
        lookup = collections.defaultdict(collections.deque)
        for i, n in enumerate(B):
            lookup[n].append(i)
        result = []
        for n in A:
            result.append(lookup[n].popleft())
        return result