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Nested list in C++ STL

  • Last Updated : 18 Sep, 2018

list in STL is used to represent a linked list in C++. How to create a nested list. We are given n lists, we need to create a list of n lists.

Examples:

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Input :  Number of lists: 2
1st list: {1 2}
2nd list:  {3 4 5 6
Output : 
[
  [ 1  2 ]
  [ 3  4  5  6 ]
]

Input : Number of lists: 3
1st list : {0 1} 
2nd list : {1 2 3}
3rd list : {2 3 4 5}
Output :
[
  [ 0  1 ]
  [ 1  2  3 ]
  [ 2  3  4  5 ]
]




// c++ program for nested list
  
#include <iostream>
#include <iterator>
#include <list>
using namespace std;
  
void printNestedList(list<list<int> > nested_list)
{
    cout << "[\n";
  
    // nested_list`s iterator(same type as nested_list)
    // to iterate the nested_list
    list<list<int> >::iterator nested_list_itr;
  
    // Print the nested_list
    for (nested_list_itr = nested_list.begin();
         nested_list_itr != nested_list.end();
         ++nested_list_itr) {
  
        cout << "  [";
  
        // normal_list`s iterator(same type as temp_list)
        // to iterate the normal_list
        list<int>::iterator single_list_itr;
  
        // pointer of each list one by one in nested list
        // as loop goes on
        list<int>& single_list_pointer = *nested_list_itr;
  
        for (single_list_itr = single_list_pointer.begin();
             single_list_itr != single_list_pointer.end();
             single_list_itr++) {
            cout << " " << *single_list_itr << " ";
        }
        cout << "]\n";
    }
    cout << "]";
}
  
// Driver code
int main()
{
    // instead integer type can have any data type
    list<list<int> > nested_list;
    list<int> single_list;
    int n, m, num;
  
    // number of lists in nested list
    n = 3;
  
    for (int i = 0; i < n; i++) {
  
        // number of elements in list
        m = i + 2;
        for (int j = 0; j < m; j++) {
            num = i + j;
            single_list.push_back(num);
        }
  
        nested_list.push_back(single_list);
  
        // delete all elements from single_list
        single_list.erase(single_list.begin(),
                          single_list.end());
    }
  
    printNestedList(nested_list);
  
    return 0;
}
Output:
[
  [ 0  1 ]
  [ 1  2  3 ]
  [ 2  3  4  5 ]
]



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