Grokking the Coding Interview: Patterns for Coding Questions

Solution: Ceiling of a Number

## Problem Statement

Given an array of numbers sorted in an ascending order, find the ceiling of a given number ‘key’. The ceiling of the ‘key’ will be the smallest element in the given array greater than or equal to the ‘key’.

Write a function to return the index of the ceiling of the ‘key’. If there isn’t any ceiling return -1.

**Example 1**:
```
Input: [4, 6, 10], key = 6
Output: 1
Explanation: The smallest number greater than or equal to '6' is '6' having index '1'.
```

**Example 2**:
```
Input: [1, 3, 8, 10, 15], key = 12
Output: 4