math - How do I return the intersection of two lists including duplicates in mathematica? -

how find intersection of 2 lists including duplicates in mathematica?

so, if have this:

list1 = {1, 1, 3, 4, 5, 6, 6, 6, 7, 7, 10, 11, 11}; list2 = {1, 1, 4, 5, 5, 6, 6, 7, 7, 8, 11, 11, 13, 14};

i'd want return this:

intersectionincludingduplicates[list1, list2] = {1, 1, 4, 5, 6, 6, 7, 7, 11, 11}

thanks , help!

here's 1 way:

catenate@keyvaluemap[constantarray]@   mapthread[min, keyintersection[counts /@ {list1, list2}]]

breaking down:

count how many times each element occurs in each list (counts)
retain elements occur in both (keyintersection)
take smaller number of occurrences (mapthread, min) , replicate given element many times (constantarray)

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