freeCodeCamp/problem-316-numbers-in-decimal-expansions.english.md at 92377cf71af628cb5ea6b28ff7d6fa66a9b52449

mrugesh 22afc2a0ca feat(learn): python certification projects (#38216 )

Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>
Co-authored-by: Kristofer Koishigawa <scissorsneedfoodtoo@gmail.com>
Co-authored-by: Beau Carnes <beaucarnes@gmail.com>

2020-05-27 13:19:08 +05:30

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id, challengeType, isHidden, title, forumTopicId

id	challengeType	isHidden	title	forumTopicId
5900f4a81000cf542c50ffbb	5	false	Problem 316: Numbers in decimal expansions	301972

Description

Let p = p1 p2 p3 ... be an infinite sequence of random digits, selected from {0,1,2,3,4,5,6,7,8,9} with equal probability. It can be seen that p corresponds to the real number 0.p1 p2 p3 .... It can also be seen that choosing a random real number from the interval [0,1) is equivalent to choosing an infinite sequence of random digits selected from {0,1,2,3,4,5,6,7,8,9} with equal probability.

For any positive integer n with d decimal digits, let k be the smallest index such that pk, pk+1, ...pk+d-1 are the decimal digits of n, in the same order. Also, let g(n) be the expected value of k; it can be proven that g(n) is always finite and, interestingly, always an integer number.

For example, if n = 535, then for p = 31415926535897...., we get k = 9 for p = 355287143650049560000490848764084685354..., we get k = 36 etc and we find that g(535) = 1008.

Given that , find

Note: represents the floor function.

Instructions

Tests

tests:
  - text: <code>euler316()</code> should return 542934735751917760.
    testString: assert.strictEqual(euler316(), 542934735751917760);

Challenge Seed

function euler316() {
  // Good luck!
  return true;
}

euler316();

Solution

// solution required

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