LeetCode-Solutions/C++/flatten-2d-vector.cpp at master · spotpan/LeetCode-Solutions · GitHub

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// Time: O(1)

// Space: O(1)

class Vector2D {

public:

Vector2D(vector<vector<int>>& vec2d) : vec(vec2d) {

x = vec.begin();

if (x != vec.end()) {

y = x->begin();

adjustNextIter();

}

int next() {

const auto ret = *y;

++y;

adjustNextIter();

return ret;

}

bool hasNext() {

return x != vec.end() && y != x->end();

}

void adjustNextIter() {

while (x != vec.end() && y == x->end()) {

++x;

if (x != vec.end()) {

y = x->begin();

}

private:

vector<vector<int>>& vec;

vector<vector<int>>::iterator x;

vector<int>::iterator y;

};