# Closest Numbers

See the original problem on HackerRank.

## Solutions

Sorting the sequence is the key to solve this challenge.

Here is a C++ Solution based on zip | map | reduce pattern:

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  #include #include #include #include #include #include using namespace std; int main() { int N; cin >> N; vector v; v.reserve(N); copy_n(istream_iterator(cin), N, back_inserter(v)); sort(begin(v), end(v)); auto minDiff = inner_product(next(begin(v)), end(v), begin(v), numeric_limits::max(), [](int curr, int nxt){ return min(curr, nxt); }, minus<>{} ); equal(begin(v), end(v)-1, begin(v)+1, [=](int l, int r){ if (abs(r-l) == minDiff) cout << l << " " << r << " "; return true; }); } 

Here is a Javascript solution by Simone Busoli:

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31  function processData(input) { const numbers = input.split('\n')[1].split(' ').map(Number).sort((a, b) => a - b) let diff = Math.abs(numbers[numbers.length-1] - numbers[0]) let output = [] for(let i = 0; i < numbers.length - 1; i++) { const newDiff = Math.abs(numbers[i] - numbers[i+1]) if(newDiff < diff) { diff = newDiff output = [numbers[i], numbers[i+1]] } else if(newDiff === diff) { output.push(numbers[i], numbers[i+1]) } } console.log(output.join(' ')) } process.stdin.resume(); process.stdin.setEncoding("ascii"); _input = ""; process.stdin.on("data", function (input) { _input += input; }); process.stdin.on("end", function () { processData(_input); }); 

An Haskell solution by Alessandro Pezzato

Sort the list, make a list of pairs of adjacent numbers, calculate differences between them and filter the list, takin only pairs where the difference is equal to the minimum. We use list comprehension and pattern matching to filter and translate pairs to lists of two elements, so they can be concatenated by concat.

  1 2 3 4 5 6 7 8 9 10 11 12  import Data.List (sort) closestNumbers :: [Int] -> [Int] closestNumbers xs = concat $[[x, y] | ((x, y), d) <- zip pairs diffs, d == minimum diffs] where sorted = sort xs pairs = zip sorted (tail sorted) diffs = (uncurry . flip) (-) <$> pairs main = interact (unwords . fmap show . closestNumbers . fmap read . tail . words) 

A C solutyion by Michele Liberi

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43  void mergesort(int *a, int n) { int m, sz, i, l, r, k, *b; if (n>1){ m=n/2, mergesort(a, m), mergesort(a+m, n-m); sz=m*sizeof(int), b=malloc(sz); memcpy(b,a,sz); l=i=0, r=m, k=0; while (la[r]) a[i++]=a[r++]; else ++l, a[i++]=b[k++]; free(b); } } int main() { int n, i, *A, m, mindif; scanf("%d\n", &n); A=malloc(n*sizeof(int)); for (i=0; i

A Swift solution by Pietro Basso

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16  func closestNumbers(arr: [Int]) -> [Int] { let array = arr.sorted() let couples = zip(array, array.dropFirst()) var result = [Int]() var currentMin = 10000000 for (lhs, rhs) in couples { let min = abs(lhs - rhs) if min < currentMin { currentMin = min result = [lhs, rhs] } else if min == currentMin { result.append(contentsOf: [lhs, rhs]) } } return result } 
We've worked on this challenge in these gyms: modena  padua  milan