pre4.java

/*
Given a non-empty array of ints, return a new array containing the elements from the original array that come before the first 4 in the original array. The original array will contain at least one 4. Note that it is valid in java to create an array of length 0.

pre4([1, 2, 4, 1]) → [1, 2]
pre4([3, 1, 4]) → [3, 1]
pre4([1, 4, 4]) → [1]
*/
public int[] pre4(int[] nums) {
  int l = Arrays.binarySearch(nums, 4);
  int[] ar =  new int[l];
  for(int i=0; i < l; i++) {
    ar[i] = nums[i];
  }
  return ar;
}