Flatten 2D Vector in C++

Suppose we have a 2D vector, we have to design and implement an iterator to flatten that 2d vector. There will be different methods as follows −
next() − This will return the next element of the current element
next() − This will return the next element of the current element
hasNext() − This will check whether next element is present or not
hasNext() − This will check whether next element is present or not
So, if the input is like [[1,2],[3],[4]] then if we call the functions as follows −
iterator.next();
iterator.next();
iterator.next();
iterator.next();
iterator.next();
iterator.next();
iterator.hasNext();
iterator.hasNext();
iterator.hasNext();
iterator.hasNext();
iterator.next();
iterator.next();
iterator.hasNext();
iterator.hasNext();
then the output will be [1,2,3,true, true,4,false]
To solve this, we will follow these steps −
Define one 2D array v
Define one 2D array v
Define initializer this will take one 2D array v,
Define initializer this will take one 2D array v,
rowPointer := 0
rowPointer := 0
colPointer := 0
colPointer := 0
n := size of v
n := size of v
while (rowPointer < n and colPointer >= size of v[rowPointer]), do −(increase rowPointer by 1)
while (rowPointer < n and colPointer >= size of v[rowPointer]), do −
(increase rowPointer by 1)
(increase rowPointer by 1)
Define a function next()
Define a function next()
x := v[rowPointer, colPointer]
x := v[rowPointer, colPointer]
(increase colPointer by 1)
(increase colPointer by 1)
if colPointer is same as size of v[rowPointer], then −colPointer := 0(increase rowPointer by 1)while (rowPointer < n and colPointer >= size of v[rowPointer]), do −(increase rowPointer by 1)
if colPointer is same as size of v[rowPointer], then −
colPointer := 0
colPointer := 0
(increase rowPointer by 1)
(increase rowPointer by 1)
while (rowPointer < n and colPointer >= size of v[rowPointer]), do −(increase rowPointer by 1)
while (rowPointer < n and colPointer >= size of v[rowPointer]), do −
(increase rowPointer by 1)
(increase rowPointer by 1)
return x
return x
Define a function hasNext()
Define a function hasNext()
return false when rowPointer is same as n
return false when rowPointer is same as n
Let us see the following implementation to get better understanding −
 Live Demo
#include <bits/stdc++.h>
using namespace std;
class Vector2D {
public:
   int rowPointer, colPointer;
   int n;
   vector<vector<int< > v;
   Vector2D(vector<vector<int< >& v){
      this->v = v;
      rowPointer = 0;
      colPointer = 0;
      n = v.size();
      while (rowPointer < n && colPointer >= v[rowPointer].size()){
         rowPointer++;
      }
   }
   int next(){
      //cout << rowPointer << " " << colPointer << endl;
      int x = v[rowPointer][colPointer];
      colPointer++;
      if (colPointer == v[rowPointer].size()) {
         colPointer = 0;
         rowPointer++;
         while (rowPointer < n && colPointer >= v[rowPointer].size()) {
            rowPointer++;
         }
      }
      return x;
   }
   bool hasNext(){
      return !(rowPointer == n);
   }
};
main(){
   vector<vector<int<> v = {{1,2},{3},{4}};
   Vector2D ob(v);
   cout << (ob.next()) << endl;
   cout << (ob.next()) << endl;
   cout << (ob.next()) << endl;
   cout << (ob.hasNext()) << endl;
   cout << (ob.next()) << endl;
   cout << (ob.hasNext());
}
ob.next()
ob.next()
ob.next()
ob.hasNext()
ob.next()
ob.hasNext()
1
2
3
1
4
0