Problem

Design and implement a data structure for a compressed string iterator. It should support the following operations: next and hasNext.

The given compressed string will be in the form of each letter followed by a positive integer representing the number of this letter existing in the original uncompressed string.

next() - if the original string still has uncompressed characters, return the next letter; Otherwise return a white space.

hasNext() - Judge whether there is any letter needs to be uncompressed.

Note:

Please remember to RESET your class variables declared in StringIterator, as static/class variables are persisted across multiple test cases. Please see here for more details.

Example:

StringIterator iterator = new StringIterator("L1e2t1C1o1d1e1");iterator.next(); // return 'L'iterator.next(); // return 'e'iterator.next(); // return 'e'iterator.next(); // return 't'iterator.next(); // return 'C'iterator.next(); // return 'o'iterator.next(); // return 'd'iterator.hasNext(); // return trueiterator.next(); // return 'e'iterator.hasNext(); // return falseiterator.next(); // return ' '

Solution

class StringIterator {    Queue
    
      queue;    public StringIterator(String str) {        queue = new LinkedList<>();        int i = 0, len = str.length();        while (i < len) {            int j = i+1;            while (j < len && Character.isDigit(str.charAt(j))) j++;                        char ch = str.charAt(i);            int count = Integer.parseInt(str.substring(i+1, j));            queue.offer(new Node(ch, count));                        i = j;        }    }    public char next() {        if (!hasNext()) return ' ';        Node node = queue.peek();        node.count--;        if (node.count == 0) queue.poll();        return node.val;    }    public boolean hasNext() {        return !queue.isEmpty();    }}class Node {    char val;    int count;    public Node(char c, int n) {        this.val = c;        this.count = n;    }}