#include <iostream>
#include <vector>

using namespace std;


int main()
{
   
	vector<vector<int>> A;
	vector<int> B;

	B.push_back(0);
	B.push_back(1);
	B.push_back(2);
	B.push_back(3);
	A.push_back(B);

	//注意需要清空B
	B.clear();
	B.push_back(4);
	B.push_back(5);
	B.push_back(6);
	B.push_back(7);
	A.push_back(B);
	
	for (int i = 0; i < A.size(); i++)
	{
   
		for (int j = 0; j < A[i].size();j++)
			cout << A[i][j] << " ";

		cout << endl;
	}

	return  0;
}

https://www.cnblogs.com/chay/p/10304485.html