int up = 0, down = matrix.size()-1;

int left = 0, right = matrix[0].size()-1;

vector<int> res;

while (left <= right && up <= down) {

for (int i=left; i<=right; i++) {

res.push_back(matrix[up][i]);

}

up++;

for (int i=up; i<=down; i++) {

res.push_back(matrix[i][right]);

}

right--;

if (up <= right) { // notice this if

for (int i=right; i>=left; i--) {

res.push_back(matrix[down][i]);

}

down--;

}

if (left <= right) {

for (int i=down; i>=up; i--) {

res.push_back(matrix[i][left]);

}

left++;

}

}

return res;

vector<vector<int> > matrix = { {1}, {2}, {3}, {4}, {5}};

vector<int> res = printMatrix(matrix);

printArray(res);

return 0;