2 d vector size() operator use

#1

how to initialize a 2d vector and what will vector.size() then denote??row or coln??

#2

Hi @khushipriya681, to make a 2D vector follow the following syntax:

vector < vector < data_type > >   vector_name ;

For ex to make a 2D vector of int named ‘v’ use:

vector < vector < int > > v ;

NOTE: Always remeber to keep the 2 '>'s in end apart by atleast 1 space because if you put them together it will mean something else.

Now here if you wright v.size() it will give you no. of rows.
Also remeber that you have created a vector of vectors and vector’s size is dynamic so for a 2d vector no. of columns of 2 vectors in it for ex:

v[i].size and v[j].size() provided i!=j

need not to be same.

Hope this helps :slight_smile:

#3

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#4

how can we assign values in a 2d array using push_back() function??please give an example

#5

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#6

Hi @khushipriya681, a 2D vector is acually a vector of vectors of something.
So in general when we make a

vector < int > v ;
…
…
v.push_back(12) ;

that means v is a vector of ints and we can push ints in it, i.e. we are pushing that element inside vector v which it was asked to be made of.

Similarly, if we declare:

vector < vector < int > > v2d ;

, this means we are making a vector of vectors of ints.

Now , just like we were pushing int type of data in v, similarly we can push v type of materials in v2d. i.e.

vector < vector < int > > v2d ;
…
…
v2d.push_back(v) ;

Apologies for late reply. Hope this helps :slight_smile:.