public class Solution {
  public int closest(int[] array, int target) {
    // Write your solution here
    if (array == null || array.length == 0) {
      return -1;
    }
    int left = 0;
    int right = array.length - 1;
    while (left + 1 < right) {
      int mid = left + (right - left) / 2;
      if (array[mid] == target) {
        return mid;
      } else if (array[mid] > target) {
        right = mid;
      } else {
        left = mid;
      }
    }
    return Math.abs(array[left] - target) < Math.abs(array[right] - target) ? left : right;
  }
}

time: O(logn)