面试:为集合集合设计迭代器 [英] Interview: Design an iterator for a collection of collections
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问题描述
在java中设计集合集合的迭代器。迭代器应该隐藏嵌套,允许您遍历属于所有集合的所有元素,就像您使用单个集合一样。
Design an iterator for a collection of collections in java. The iterator should hide the nesting, allowing you to iterate all of the elements belonging to all of the collections as if you were working with a single collection
推荐答案
这是一个可能的实现。注意,我离开remove()未实现:
Here is a possible implementation. Note that I left remove() unimplemented:
public class MultiIterator <T> implements Iterator<T>{
private Iterator<? extends Collection<T>> it;
private Iterator<T> innerIt;
private T next;
private boolean hasNext = true;
public MultiIterator(Collection<? extends Collection<T>> collections) {
it = collections.iterator();
prepareNext();
}
private void prepareNext() {
do {
if (innerIt == null || !innerIt.hasNext()) {
if (!it.hasNext()) {
hasNext = false;
return;
} else
innerIt = it.next().iterator();
}
} while (!innerIt.hasNext());
next = innerIt.next();
}
@Override
public boolean hasNext() {
return hasNext;
}
@Override
public T next() {
if (!hasNext)
throw new NoSuchElementException();
T res = next;
prepareNext();
return res;
}
@Override
public void remove() {
//TODO
}
}
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