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flatten-nested-list-iterator_1_AC.cpp
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flatten-nested-list-iterator_1_AC.cpp
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// That was pretty ugly.
// One of the most foolish feature in C++ is the write-once reference.
// I don't see why they forbid reference reassignent.
/**
* // 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) {
if (nestedList.size() == 0) {
return;
}
arr.push(&nestedList);
pos.push(0);
}
int next() {
prepareNext();
int res = (*arr.top())[pos.top()].getInteger();
++pos.top();
return res;
}
bool hasNext() {
prepareNext();
return !arr.empty();
}
private:
stack<const vector<NestedInteger> *> arr;
stack<int> pos;
void prepareNext() {
const vector<NestedInteger> *plist;
while (!arr.empty()) {
while (pos.top() < arr.top()->size() && !((*arr.top())[pos.top()].isInteger())) {
plist = &((*arr.top())[pos.top()].getList());
arr.push(plist);
pos.push(0);
}
while (pos.top() == arr.top()->size()) {
arr.pop();
pos.pop();
if (arr.empty()) {
break;
} else {
++pos.top();
}
}
if (arr.empty() || ((pos.top() < arr.top()->size() && (*arr.top())[pos.top()].isInteger()))) {
break;
}
}
}
};
/**
* Your NestedIterator object will be instantiated and called as such:
* NestedIterator i(nestedList);
* while (i.hasNext()) cout << i.next();
*/