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+#!/usr/bin/python3
+# https://theweeklychallenge.org/blog/perl-weekly-challenge-245/#TASK2
+#
+# Task 2: Largest of Three
+# ========================
+#
+# You are given an array of integers >= 0.
+#
+# Write a script to return the largest number formed by concatenating some of
+# the given integers in any order which is also multiple of 3. Return -1 if
+# none found.
+#
+## Example 1
+##
+## Input: @ints = (8, 1, 9)
+## Output: 981
+##
+## 981 % 3 == 0
+#
+## Example 2
+##
+## Input: @ints = (8, 6, 7, 1, 0)
+## Output: 8760
+#
+## Example 3
+##
+## Input: @ints = (1)
+## Output: -1
+#
+############################################################
+##
+## discussion
+##
+############################################################
+#
+# While all examples in the description use single-digit numbers,
+# there is nothing that would require this. So in order to catch all
+# solutions, we need all possible permutations of all subsets of the
+# array and of the numbers created out of those we need the biggest
+# one that is divisible by 3.
+
+from itertools import chain, combinations, permutations
+
+def powerset(iterable):
+    "powerset([1,2,3]) → () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)"
+    s = list(iterable)
+    return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))
+
+def largest_of_three(ints: list):
+    print("Input: (", ", ".join(str(x) for x in ints), ")")
+    result = int()
+    for myset in powerset(ints):
+        for c in permutations(myset, len(myset)):
+            v = str("".join(str(x) for x in c))
+            # print("-> ", v)
+            if len(v) > 0:
+                # print("Considering", v, "as a value")
+                value = int(v)
+                if value % 3 == 0:
+                    if len(str(result)) == 0:
+                        result = value
+                    if value > result:
+                        result = value
+    if len(str(result)) == 0:
+        print("Output: -1")
+    else:
+        print("Output:", str(result))
+
+largest_of_three([8, 1, 9]);
+largest_of_three([8, 6, 7, 1, 0]);
+largest_of_three([1]);
+largest_of_three([8, 60, 7]);
+largest_of_three([80, 6, 7]);
+