Lifion Array Intersection

intersection.js

function intersection(a, b) {
  a = quickSort(a);
  b = quickSort(b);
  let results = [];

  for(let i = 0; i < a.length; i++) {
    let current = a[i];
    let triedThis;

    if(current == a[i - 1]) {
      triedThis = true;
    } else {
      triedThis = false;
    }

    if(triedThis == false) {
      let hi = b.length;

      while(hi >= 0) {
        let mid = Math.floor(hi / 2);

        if(b[mid] == current) {
          results.push(current);
          b = b.slice(mid + 1);
          break;
        } else if(b[mid] < current) {
          b = b.slice(mid + 1);
        } else {
          hi = mid - 1;
        }
      }
    }
  }

  return results;
}


function quickSort(array) {
  if(array.length < 2) {
    return array;
  }

  let pivot = array[0];
  let l = [];
  let g = [];

  for(let i = 1; i < array.length; i++) {
    array[i] < pivot ? l.push(array[i]) : g.push(array[i]);
    }
  

  return quickSort(l).concat(pivot, quickSort(g));
}

console.log(intersection([1, 2, 3], [1, 2]));
console.log(intersection([], [1, 2]));
console.log(intersection([1], [3, 2]));
console.log(intersection([1], [3, 2, 1]));
console.log(intersection([4, 4, 4], [4, 4, 4]));
console.log(intersection([4, 4, 4, 5, 6], [4, 4, 4, 5]));