How to implement 2D vector array?

Question

I\'m using the vector class in the STL library for the first time. How should I add to a specific row of the vector array?

struct x{
     vector 

        

Answer 1

Just use the following methods to create a 2-D vector.

int rows, columns;        

// . . .

vector < vector < int > > Matrix(rows, vector< int >(columns,0));

OR

vector < vector < int > > Matrix;

Matrix.assign(rows, vector < int >(columns, 0));

//Do your stuff here...

This will create a Matrix of size rows * columns and initializes it with zeros because we are passing a zero(0) as a second argument in the constructor i.e vector < int > (columns, 0).

Answer 2

vector<int> adj[n]; // where n is number of rows in 2d vector.

Answer 3

Another way to define a 2-d vector is to declare a vector of pair's.

 vector < pair<int,int> > v;

**To insert values**
 cin >> x >>y;
 v.push_back(make_pair(x,y));

**Retrieve Values**
 i=0 to size(v)
 x=v[i].first;
 y=v[i].second;

For 3-d vectors take a look at tuple and make_tuple.