CeilingFloor.java

package com.datastructures;

public class CeilingFloor {

  static int findCeiling(int[] arr, int target) {
    int start = 0, end = arr.length - 1;
    while (start <= end) {
      int mid = start + (end - start) / 2;
      if (target < arr[mid]) {
        end = mid - 1;
      } else if (target > arr[mid]) {
        start = mid + 1;
      } else {
        return arr[mid];
      }
    }
    return arr[start];
  }

  static int findFloor(int arr[], int target) {
    int start = 0, end = arr.length - 1;
    while (start <= end) {
      int mid = start + (end - start) / 2;
      if (target < arr[mid]) {
        end = mid - 1;
      } else if (target > arr[mid]) {
        start = mid + 1;
      } else {
        return arr[mid];
      }
    }
    return end;
  }

  public static void main(String[] args) {
    int[] arr = {12, 18, 24, 30, 36, 42};
    System.out.println(findCeiling(arr, 18));
    System.out.println(findFloor(arr, 1));
  }
}