const findSum = (arr, val) => {
  for (let i = 0; i < arr.length; i++){
    if (binarySearch(removeIndex(arr, i), val - arr[i])) {
      return true;
    }
  };
  return false;
}; 

const removeIndex = (arr, i) => {
  return arr.slice(0, i).concat(arr.slice(i + 1, arr.length));
};

const binarySearch = (arr, val) => {
  let start = 0;
  let end = arr.length - 1;
  let pivot = Math.floor(arr.length / 2);  
  while (start < end) {
    if (val < arr[pivot]) {
      end = pivot - 1;
    } else if (val > arr[pivot]) {
      start = pivot + 1;
    };
    pivot = Math.floor((start + end) / 2);
    if (arr[pivot] === val) {
      return true;
    }
  };
  return false;
};


// Tests below
describe('findSum', function() {
  
  it('returns TRUE if adding two numbers in an array yield the given value', () => {
    expect(findSum([1, 2, 4, 4], 8)).toEqual(true); 
  });
  
it('returns FALSE if adding two numbers in an array does not yield the given value', () => {  
    expect(findSum([1, 2, 5, 9], 8)).toEqual(false);
  });
  
  it('does not count any value twice', () => {
    expect(findSum([1, 2, 4, 9], 8)).toEqual(false);
    expect(findSum([1, 2, 5, 6], 12)).toEqual(false);
  });
  
  it('can handle negative values', () => {
    expect(findSum([-2, 1, 1, 4], 2)).toEqual(true);
    expect(findSum([-3, -2, 1, 4], -5)).toEqual(true);
    expect(findSum([-7, -3, -2, -1], -8)).toEqual(true);  
  });
  
  it('can handle zero values', () => {
    expect(findSum([-2, 0, 0, 1], 0)).toEqual(true);
    expect(findSum([0, 0, 0, 0], 0)).toEqual(true);
    expect(findSum([-1, 0, 1, 2], 0)).toEqual(true);  
  });
});