Arithmetic expression construction
When can n given numbers be combined using arithmetic operators from a given subset of {+,−,×,÷} to obtain a given target number? We study three variations of this problem of Arithmetic Expression Construction: when the expression (1) is unconstrained; (2) has a specified pattern of parentheses and...
Main Authors: | , , , , , , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
2022-07-22T14:19:40Z.
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Subjects: | |
Online Access: | Get fulltext |
Summary: | When can n given numbers be combined using arithmetic operators from a given subset of {+,−,×,÷} to obtain a given target number? We study three variations of this problem of Arithmetic Expression Construction: when the expression (1) is unconstrained; (2) has a specified pattern of parentheses and operators (and only the numbers need to be assigned to blanks); or (3) must match a specified ordering of the numbers (but the operators and parenthesization are free). For each of these variants, and many of the subsets of {+,−,×,÷}, we prove the problem NP-complete, sometimes in the weak sense and sometimes in the strong sense. Most of these proofs make use of a rational function framework which proves equivalence of these problems for values in rational functions with values in positive integers. |
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