Problem 1472. nth Rational Number

Created by G K in Community

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Return the nth rational number.

This is the inverse to Problem 1471. Index of a Rational number

The first ten positive rational numbers under the enumeration using cantors diagonalization argument are 1/1, 2/1, 1/2, 3/1, 2/2, 1/3, 4/1, 3/2, 2/3, 1/4.

Find the index of a positive rational number enumerated in this manner, i.e. the 6th rational number is 1/3.

Problem 2) Prev: 1471 Next: 1477

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Last solution submitted on Jun 07, 2019

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2 Comments

2 Comments

Massimo Zanetti on 7 Oct 2016

Is that possible to have a ranking of the solutions based on their performing time? I think that the could be a method that is fast even if more sized.

Massimo Zanetti on 10 Oct 2016

Solution

provides inexpensive method. There is only one 2nd order polynomial solution and one division.

Solution Comments

Solution 823670

1 Comment

1 Comment

ABDELRAHMAN on 10 Feb 2016

i get the same solution but the test says false
for test 9, 11

Solution 748363

1 Comment

1 Comment

Richard on 28 Sep 2015

I thought we had to discount all the equivalent fractions (like 2/2) so I wrote this horrible cheat. How embarrassing.

Problem 1472. nth Rational Number

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Problem 1472. nth Rational Number

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Last 200 Solutions

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Recent Solvers99

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