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 true
iterator.next(); // return 'e'
iterator.hasNext(); // return false
iterator.next(); // return ' '
Solution
class StringIterator {
Queue<Node> 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;
}
}
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