# GeetCode Hub

Design the `CombinationIterator` class:

• `CombinationIterator(string characters, int combinationLength)` Initializes the object with a string `characters` of sorted distinct lowercase English letters and a number `combinationLength` as arguments.
• `next()` Returns the next combination of length `combinationLength` in lexicographical order.
• `hasNext()` Returns `true` if and only if there exists a next combination.

Example 1:

```Input
["CombinationIterator", "next", "hasNext", "next", "hasNext", "next", "hasNext"]
[["abc", 2], [], [], [], [], [], []]
Output
[null, "ab", true, "ac", true, "bc", false]

Explanation
CombinationIterator itr = new CombinationIterator("abc", 2);
itr.next();    // return "ab"
itr.hasNext(); // return True
itr.next();    // return "ac"
itr.hasNext(); // return True
itr.next();    // return "bc"
itr.hasNext(); // return False
```

Constraints:

• `1 <= combinationLength <= characters.length <= 15`
• All the characters of `characters` are unique.
• At most `104` calls will be made to `next` and `hasNext`.
• It's guaranteed that all calls of the function `next` are valid.

class CombinationIterator { public CombinationIterator(String characters, int combinationLength) { } public String next() { } public boolean hasNext() { } } /** * Your CombinationIterator object will be instantiated and called as such: * CombinationIterator obj = new CombinationIterator(characters, combinationLength); * String param_1 = obj.next(); * boolean param_2 = obj.hasNext(); */