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:
Input: [[1,1],2,[1,1]]
Output: [1,1,2,1,1]
Explanation: By calling next repeatedly until hasNext returns false,
the order of elements returned by next should be: [1,1,2,1,1].
Example 2:
Input: [1,[4,[6]]]
Output: [1,4,6]
Explanation: By calling next repeatedly until hasNext returns false,
the order of elements returned by next should be: [1,4,6].
class NestedIterator {
public:
NestedIterator(vector<NestedInteger> &nestedList) {
for (int i = nestedList.size() - 1; i >= 0; --i) {
st.push(nestedList[i]);
}
}
int next() {
NestedInteger t = st.top(); st.pop();
return t.getInteger();
}
bool hasNext() {
while (!st.empty()) {
NestedInteger t = st.top();
if (t.isInteger()) return true;
st.pop();
vector<NestedInteger> list = t.getList();
for (int i = list.size() - 1; i >= 0; --i) {
st.push(list[i]);
}
}
return false;
}
stack<NestedInteger> st;
};