This program illustrates the use of the STL find_end() algorithm to find
the last occurrence of one range of matching integer values in a vector
within another range of integer values, also in a vector, and where
corresponding values match if and only if they have the same digit sum.
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Here are the contents of v1:
17 21 13 5 6 7 8 12 31 14 9 10 11
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Here are the contents of v2:
21 13 5
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The last instance of v2 in v1 begins at location 8.
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