Solution URL
https://leetcode.com/submissions/detail/412787883/
代码
/**
* // This is the interface that allows for creating nested lists.
* // You should not implement it, or speculate about its implementation
* public 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();
* }
*/
public class NestedIterator implements Iterator<Integer> {
Stack<Integer> s1 = new Stack<>();
Stack<Integer> s2 = new Stack<>();
public NestedIterator(List<NestedInteger> nestedList) {
helper(nestedList);
while(!s1.isEmpty()){
s2.push(s1.pop());
}
}
@Override
public Integer next() {
return s2.pop();
}
@Override
public boolean hasNext() {
return !s2.isEmpty();
}
public void helper(List<NestedInteger> nl){
for(NestedInteger temp: nl){
if(temp.isInteger()){
s1.push(temp.getInteger());
}else{
helper(temp.getList());
}
}
}
}
/**
* Your NestedIterator object will be instantiated and called as such:
* NestedIterator i = new NestedIterator(nestedList);
* while (i.hasNext()) v[f()] = i.next();
*/
