contains.java

static boolean contains (int[] h, int n) {
  int low = 0;
  int high = h.length;
  int d;
  do {
     d = (high - low) / 2;
    int mid = low + d;
    if (h[mid] == n) {
      return true;
    } else if (h[mid] < n) {
      low = mid;
    } else {
      high = mid;
    }
  } while (d > 0);
  return false;
}

Determine if a needle is in a haystack.
Haystack needs to be sorted beforehand.
Complexity should be O(log n) since we're not searching the whole of the haystack for the needle