6kyu_Coding3Min_CollatzArray(SplitOrMerge).js

// 6kyu - Coding 3min: Collatz Array(Split or merge)

// This is the simple version of Shortest Code series. If you need some challenges, 
// please try the challenge version

// #Task:

// Give you an number array ```arr```, and a number ```n```(n>=0), In accordance with 
// the rules of kata, returns the array after ```n``` times changes .

// Rules: In every time of change, when the element of array is an odd number, it 
// changed by ```x*3+1```(element is x), and merge with next element 
// ```arr[i]+arr[i+1]```(i is index of element, if it's the last element of array, do 
// 	not merge with other element);when the element is a even number, changed by 
// ```x=x/2```,and split to two element.

// Example: 
//     arr=[3,4,5]
//     n=0: [3,4,5]
//     n=1: [14,16] 
//     element1=>3*3+1==10, then merge element2, 10+4=14; 
//     element2 merged by element1, so element2 disappeared;
//     element3=>5*3+1==16, no element merge
//     n=2: [7,7,8,8]
//     element1 split into 7,7; element1 split into 8,8;
//     n=3: [29,4,4,4,4]
//     n=4: [92,2,2,2,2,2,2]
//     n=5: [46,46,1,1,1,1,1,1,1,1,1,1,1,1]
//     n=6: [23,23,23,23,5,5,5,5,5,5]
//     n=... [...]


function sc(arr,n) {
  let res = [];
  for(let i=0;i<arr.length;i++)
    (arr[i] % 2 === 1) ? res.push(arr[i++] * 3+1 + (arr[i]||0)) : res.push(arr[i]/2,arr[i]/2)
  return (n) ? sc(res,n-1):arr;
}