Given an integer array, the goal is to find the ceiling on the right for each element - the smallest number greater than or equal to it that appears after it. If no such number exists, return -1.
Example:
Input: arr[] = {10, 100, 200, 30, 120, 120}
Output: 30 120 -1 120 120 -1
Naive Approach
Follow the steps to find the ceiling of each element using the naive approach:
- Traverse the array from left to right.
- For each element, initialize a variable ceil as -1.
- Compare the current element with all elements to its right.
- Update ceil if a right-side element is ≥ current element and < current ceil (or if ceil is -1).
- After checking all elements to the right, print or store the value of ceil.
- Repeat the process for all elements in the array.
Implementation
Output30 120 -1 120 120 -1
Efficient Approach Using TreeSet
Follow the below steps to find the ceiling of each element on its right side using a TreeSet:
- Initialize a TreeSet to keep track of elements seen so far.
- Create a result array to store the ceiling of each element.
- Traverse the input array from right to left.
- For each element, use TreeSet.ceiling(element) to find the smallest element greater than or equal to it.
- If a ceiling exists, store it in the result array; otherwise, store -1.
- Add the current element to the TreeSet so that future elements can find their ceiling.
- After processing all elements, print or return the result array.
Implementation
