原题链接在这里：https://leetcode.com/problems/design-compressed-string-iterator/description/
题目：
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 ' '
题解：
用 index 标记当前s位置. 用count计数之前char出现的次数. 当count--到0时继续向后移动 index.
Time Complexity: hasNext(), O(1). next(), O(n). n= compressedString.length().
Space: O(1).
AC Java:
class StringIterator {
String s;
int index;
char cur;
int count;
public StringIterator(String compressedString) {
s = compressedString;
index = 0;
count = 0;
}
public char next() {
if(count != 0){
count--;
return cur;
}
if(index >= s.length()){
return ' ';
}
cur = s.charAt(index++);
int endIndex = index;
while(endIndex<s.length() && Character.isDigit(s.charAt(endIndex))){
endIndex++;
}
count = Integer.valueOf(s.substring(index, endIndex));
index = endIndex;
count--;
return cur;
}
public boolean hasNext() {
return index != s.length() || count != 0;
}
}
/**
* Your StringIterator object will be instantiated and called as such:
* StringIterator obj = new StringIterator(compressedString);
* char param_1 = obj.next();
* boolean param_2 = obj.hasNext();
*/