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