题目链接:https://leetcode.com/problems/flatten-nested-list-iterator/?tab=Description
Given a nested list of integers, implement an iterator to flatten it.
Each element is either an integer, or a list -- whose elements may also be integers or other lists.
Example 1:
Given the list [[1,1],2,[1,1]]
,
By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,1,2,1,1]
.
Example 2:
Given the list [1,[4,[6]]]
,
By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,4,6]
.
/**
* // This is the interface that allows for creating nested lists.
* // You should not implement it, or speculate about its implementation
* class NestedInteger {
* public:
* // Return true if this NestedInteger holds a single integer, rather than a nested list.
* bool isInteger() const;
*
* // Return the single integer that this NestedInteger holds, if it holds a single integer
* // The result is undefined if this NestedInteger holds a nested list
* int getInteger() const;
*
* // Return the nested list that this NestedInteger holds, if it holds a nested list
* // The result is undefined if this NestedInteger holds a single integer
* const vector<NestedInteger> &getList() const;
* };
*/
class NestedIterator{
public:
NestedIterator(vector<NestedInteger> &nestedList)
{
vector<int> res;
for(int i=0;i<nestedList.size();i++)
flatten(nestedList[i]);
k=0;
}
int next()
{
return flat[k++];
}
bool hasNext()
{
return k<flat.size();
}
private:
vector<NestedInteger> vec;
vector<int> flat;
int k=0;
void flatten(NestedInteger n)
{
if(n.isInteger())
{
flat.push_back(n.getInteger());
return;
}
const vector<NestedInteger> v=n.getList();
for(int i=0;i<v.size();i++)
flatten(v[i]);
}
};
/**
* Your NestedIterator object will be instantiated and called as such:
* NestedIterator i(nestedList);
* while (i.hasNext()) cout << i.next();
*/