VECTOR

what is vector?

• vector is a linear data structure.
• unlike stack and queues here u can access any element you want.
• it is like arrays . If there are arrays then why a vector?

  problems with arrays:

  1. memory management.
  2. writing codes for deletion , insertion etc.. for an element in an array.

     How vector overcomes this??

     1.memory management: it uses dynamic arrays. 2.writing codes for deletion ,insertion etc.. an element in an array. we have predefined functions in vector stl.

How to use vectors?

1.How is a vector defined?

vector is a template which is included in stl

template:

vector<int> v1;
vector<char> v2;
vector<string> v3;

• above described v1,v2,v3 represents “ structures”.
• we know that structures can contain variables ,functions etc.. which can be public or private.
• we also know that we can access these using dot representaion like v.a (this gives a varible which is included in structure v).
• v.b()(this calls the function b which is include structure v).
• thus vector acts as a template or a container class by specifying the type u want like int,char etc .. it provides you structures.

How to use vector in your program: #include<vector>

intiallizing vector to get a structure; intialise the respective data type which you want as

vector<int> v1;
vector<char> v2;
vector<string> v3;

2.functions included in a vector stl?

v.push_back(a) to add element to the vector at end.

v.size()for finding size of v.

v[i] or v.at(i)for acessing element at position i.

“itr” mentioned below is an iterator.iterator is a pointer to element in the structure; vector<int>::iterator itr;

iterator initilzation
itr=v.begin()here it points to starting element of a vector.

v.insert(itr,a)inserts element a at position itr. v.erase(itr)erases the position representing itr or deletes element *itr .

v.erase(itr1,itr2) erases the positions from it1 t0 it2.

WITH USING VECTORS WE CAN IMPLEMENT STACK AND QUEUE FIND HOW??

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