22 lines
863 B
Markdown
22 lines
863 B
Markdown
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By using each of the digits from the set, `{1, 2, 3, 4}`, exactly once,
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and making use of the four arithmetic operations (`+`, `?`, `*`, `/`) and brackets/parentheses,
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it is possible to form different positive integer targets.
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For example,
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~~~
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8 = (4 * (1 + 3)) / 2
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14 = 4 * (3 + 1 / 2)
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19 = 4 * (2 + 3) ? 1
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36 = 3 * 4 * (2 + 1)
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~~~
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Note that concatenations of the digits, like `12 + 34`, are not allowed.
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Using the set, {1, 2, 3, 4}, it is possible to obtain thirty-one different target numbers
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of which 36 is the maximum, and each of the numbers 1 to 28 can be obtained
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before encountering the first non-expressible number.
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Find the set of four distinct digits, `a < b < c < d`, for which the
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longest set of consecutive positive integers, 1 to n, can be obtained,
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giving your answer as a string: abcd.
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