Package g1201_1300.s1286_iterator_for_combination

Class CombinationIterator

java.lang.Object
g1201_1300.s1286_iterator_for_combination.CombinationIterator
public class CombinationIterator extends java.lang.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
    Description
    CombinationIterator(java.lang.String characters, int combinationLength)
     

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    hasNext()
     
    java.lang.String
    next()
     

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • CombinationIterator

      public CombinationIterator(java.lang.String characters, int combinationLength)

  • Method Details

    • next

      public java.lang.String next()

    • hasNext

      public boolean hasNext()