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341.hpp
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341.hpp
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#ifndef LEETCODE_341_HPP
#define LEETCODE_341_HPP
#include <iostream>
#include <queue>
#include <algorithm>
#include <vector>
#include <unordered_map>
#include <unordered_set>
#include <set>
#include <memory>
#include <stack>
#include <numeric>
using namespace std;
/**
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(const vector<NestedInteger> &nestedList) {
begins.emplace(nestedList.begin());
ends.emplace(nestedList.end());
}
int next() {
hasNext();
return (begins.top()++)->getInteger();
}
bool hasNext() {
while (begins.size() > 0) {
if (begins.top() == ends.top()) {
begins.pop();
ends.pop();
} else {
auto x = begins.top();
if (x->isInteger()) {
return true;
}
begins.top()++;
begins.emplace(x->getList().begin());
ends.emplace(x->getList().end());
}
}
return false;
}
private:
stack<vector<NestedInteger>::const_iterator> begins, ends;
};
/**
* Your NestedIterator object will be instantiated and called as such:
* NestedIterator i(nestedList);
* while (i.hasNext()) cout << i.next();
*/
#endif //LEETCODE_341_HPP