Initialize two-dimensional vector

1.
int M = 4;
int N = 3;
vector<vector<int>> matrix(M, vector<int>(N, value));

2.
vector<int> row (N, value);
vector<vector<int>> matrix(M, row);

3.
vector<vector<int>> matrix(M);
for(int i = 0; i < M; i++)
	matrix[i].resize(N, value);

여러 방법이 있길래 정리해 보았다.