_604.java

package com.fishercoder.solutions;

import java.util.ArrayDeque;
import java.util.Deque;

/**
 * 604. Design Compressed String Iterator
 *
 * 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 true
 iterator.next(); // return 'e'
 iterator.hasNext(); // return false
 iterator.next(); // return ' '

 */
public class _604 {
    public static class Solution1 {
        public static class StringIterator {

            Deque<int[]> deque;

            public StringIterator(String compressedString) {
                deque = new ArrayDeque<>();
                int len = compressedString.length();
                int i = 0;
                while (i < len) {
                    int j = i + 1;
                    while (j < len && Character.isDigit(compressedString.charAt(j))) {
                        j++;
                    }
                    deque.addLast(new int[]{compressedString.charAt(i) - 'A', Integer.parseInt(compressedString.substring(i + 1, j))});
                    i = j;
                }
            }

            public char next() {
                if (deque.isEmpty()) {
                    return ' ';
                }
                int[] top = deque.peek();
                top[1]--;
                if (top[1] == 0) {
                    deque.pollFirst();
                }
                return (char) ('A' + top[0]);
            }

            public boolean hasNext() {
                return !deque.isEmpty();
            }
        }
    }
}