int binarySearch(int[] nums, int target){
  if(nums == null || nums.length == 0)
    return -1;

  int left = 0, right = nums.length;
  while(left < right){
    // Prevent (left + right) overflow
    int mid = left + (right - left) / 2;
    if(nums[mid] == target){ return mid; }
    else if(nums[mid] < target) { left = mid + 1; }
    else { right = mid; }
  }

  // Post-processing:
  // End Condition: left == right
  if(left != nums.length && nums[left] == target) return left;
  return -1;
}