diff options
| -rw-r--r-- | c/012-highly_divisible_triangular_number.c | 2 | ||||
| -rw-r--r-- | julia/073-counting_fractions_in_a_range.jl | 33 |
2 files changed, 34 insertions, 1 deletions
diff --git a/c/012-highly_divisible_triangular_number.c b/c/012-highly_divisible_triangular_number.c index 4ece373..c25f37d 100644 --- a/c/012-highly_divisible_triangular_number.c +++ b/c/012-highly_divisible_triangular_number.c @@ -15,7 +15,7 @@ int count_divisors(int nb) int i, div_nb = 0; for (i = 1; i <= sqrt(nb); i++) { if (nb % i == 0) - div_nb += (i != nb / i ? 2 : 1); + div_nb += (i != nb / i ? 2 : 1); // how the hell did I get there? eddie woo } return div_nb; } diff --git a/julia/073-counting_fractions_in_a_range.jl b/julia/073-counting_fractions_in_a_range.jl new file mode 100644 index 0000000..5ec6c21 --- /dev/null +++ b/julia/073-counting_fractions_in_a_range.jl @@ -0,0 +1,33 @@ +### +# Counting fractions in a range +# Problem 73 +# +# Consider the fraction, n/d, where n and d are positive integers. If n<d and HCF(n,d)=1, +# it is called a reduced proper fraction. +# If we list the set of reduced proper fractions for d ≤ 8 in ascending order of size, we +# get: +# 1/8, 1/7, 1/6, 1/5, 1/4, 2/7, 1/3, 3/8, 2/5, 3/7, 1/2, 4/7, 3/5, 5/8, 2/3, 5/7, 3/4, 4/5, +# 5/6, 6/7, 7/8 +# It can be seen that there are 3 fractions between 1/3 and 1/2. +# How many fractions lie between 1/3 and 1/2 in the sorted set of reduced proper fractions +# for d ≤ 12,000? +### + + +# HCF means Higest Common Factor (aka Greatest Common Divisor) +# HCF(n, d) is to ensure that the fraction is reduced. +# Eddie Woo GCD: https://www.youtube.com/watch?v=ui5yjN1riQA + +const TOP = 12_000 + +# ~15s +result = length( + Set([ + n // d + for d in 1:TOP + for n in 1:d + if 1 // 3 < n // d < 1 // 2 + ]) +) + +println(result) |