About the use of vector<vector<int> > in C + +

1. Definition

Vector<vector<int>> a;//Error Definition method vector<vector<int> > a;//definition

2. Inserting elements

If you want to define a = [[0,1,2],[3,4,5]], then:

Correct insertion method vector<vector<int> > A;//a.push_back must be vectorvector<int> B; B.push_back (0); B.push_back (1); B.push_back (2); A.push_back (B); B.clear (); B.push_back (3); B.push_back (4); B.push_back (5); A.push_back (B);

Wrong insertion method vector<vector<int> > A; A[0].push_back (0); A[0].push_back (1); A[0].push_back (2); A[1].push_back (3); A[1].push_back (4); A[1].push_back (5);

3. Length

The number of vector elements in vector<vector<int> >a len = a.size ();//vector<vector<int> > The length of the vector element in a, Len = A[i].size ();

　　

About the use of vector<vector<int> > in C + +