Package g1201_1300.s1286_iterator_for_combination

Class 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 Detail

      • CombinationIterator

        public CombinationIterator​(String characters,
                           int combinationLength)

    • Method Detail

      • hasNext

        public boolean hasNext()