/*
* 341. Flatten Nested List Iterator
* 2016-7-10 by Mingyang
* 这个题目又是Iterator,这里不能直接用那个东西了
* 而且我们知道List可以从最后一个往前遍历
*/
class NestedIterator implements Iterator<Integer> {
Stack<NestedInteger> stack = new Stack<>();
public NestedIterator(List<NestedInteger> nestedList) {
for(int i = nestedList.size() - 1; i >= 0; i--) {
stack.push(nestedList.get(i));
}
}
@Override
public Integer next() {
return stack.pop().getInteger();
}
@Override
public boolean hasNext() {
while(!stack.isEmpty()) {
NestedInteger curr = stack.peek();
if(curr.isInteger()) {
return true;
}
stack.pop();
for(int i = curr.getList().size() - 1; i >= 0; i--) {
stack.push(curr.getList().get(i));
}
}
return false;
}
@Override
public void remove() {
// TODO Auto-generated method stub
}
}
interface NestedInteger {
// @return true if this NestedInteger holds a single integer, rather than a nested list.
public boolean isInteger();
// @return the single integer that this NestedInteger holds, if it holds a single integer
// Return null if this NestedInteger holds a nested list
public Integer getInteger();
// @return the nested list that this NestedInteger holds, if it holds a nested list
// Return null if this NestedInteger holds a single integer
public List<NestedInteger> getList();
}