g1201_1300.s1286_iterator_for_combination

Class CombinationIterator

java.lang.Object

g1201_1300.s1286_iterator_for_combination.CombinationIterator

public class CombinationIterator
extends Object

1286 - Iterator for Combination.

Medium

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 is guaranteed that all calls of the function next are valid.

Constructor Summary

Constructors

Constructor and Description
CombinationIterator(String characters, int combinationLength)

Method Summary

Modifier and Type	Method and Description
boolean	hasNext()
String	next()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CombinationIterator

public CombinationIterator(String characters,
                           int combinationLength)

Method Detail

next

public String next()

hasNext

public boolean hasNext()