bool insert(int x, int y, int pos, unordered_map<int, unordered_map<int, int> >& edgeMap) {

int& mask = edgeMap[x][y];

if(mask & pos) {

return false;

}

mask |= pos;

return true;

}

bool isRectangleCover(vector<vector<int>>& rectangles) {

unordered_map<int, unordered_map<int, int> > edgeMap;

int top = INT_MAX, left = INT_MAX, bottom = INT_MIN, right = INT_MIN;

for(int i = 0; i < rectangles.size(); i++) {

int x1 = rectangles[i][0], y1 = rectangles[i][1];

int x2 = rectangles[i][2], y2 = rectangles[i][3];

top = min(top, x1);

left = min(left, y1);

bottom = max(bottom, x2);

right = max(right, y2);

if(!insert(x1, y1, 1, edgeMap)) {

return false;

}

if(!insert(x1, y2, 2, edgeMap)) {

return false;

}

if(!insert(x2, y1, 4, edgeMap)) {

return false;

}

if(!insert(x2, y2, 8, edgeMap)) {

return false;

}

}

bool interior[16] = {false};

interior[3] = interior[5] = interior[10] = interior[12] = interior[15] = true;

for(auto it = edgeMap.begin(); it != edgeMap.end(); ++it) {

int x = it->first;

for(auto it2 = it->second.begin(); it2 != it->second.end(); ++it2) {

int y = it2->first;

int mask = it2->second;

if( ((x != top and x != bottom) or (y != left and y != right)) and !interior[mask] ) {

return false;

}

}

}

return true;

}