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Given a list of numbers with only 3 unique numbers (1, 2, 3), sort the list in O(n) time.

Given a list of numbers with only 3 unique numbers (1, 2, 3), sort the list in O(n) time.

Example

Input: [3, 3, 2, 1, 3, 2, 1]
Output: [1, 1, 2, 2, 3, 3, 3]

Challenge

Try sorting the list using constant space.

Solution

function a(l) {
  for (var el of l) {
    if (typeof l1 === 'undefined') {
      l1 = [el];
    } else if (el === l1[0]) {
      l1.push(el);
    } else if (typeof l2 === 'undefined') {
      l2 = [el];
    } else if (el === l2[0]) {
      l2.push(el);
    } else if (typeof l3 === 'undefined') {
      l3 = [el];
    } else if (el === l3[0]) {
      l3.push(el);
    }
  }

  if (l1[0] < l2[0]) {
    if (l1[0] < l3[0]) {
      if (l2[0] < l3[0]){
        var l0 = l1.concat(l2).concat(l3);
      } else {
        var l0 = l1.concat(l3).concat(l2);
      }
    } else {
      var l0 = l3.concat(l1).concat(l2);
    }
  } else {
    if(l1[0] < l3[0]) { // l2 < l1 < l3
      var l0 = l2.concat(l1).concat(l3);
    } else if(l2[0] < l3[0]) { // l2 < l3 <l1
      var l0 = l2.concat(l3).concat(l1);
    } else { // l3 < l2 < l1
      var l0 = l3.concat(l2).concat(l1);
    }
  }
  return l0
}

 console.log(a([1,2,3,2,2,3,1,1,3]));
// console.log(a([1,3,2,2,2,3,1,1,3]));
// console.log(a([2,3,1,2,2,3,1,1,3]));
// console.log(a([2,1,3,2,2,3,1,1,3]));
// console.log(a([3,2,1,2,2,3,1,1,3]));
// console.log(a([3,1,2,2,2,3,1,1,3]));

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