whats wrong with this simple program. I want to create multi list and insert using c++ STL. its giving segmentation fault.
#include <iostream>
#include <list>
using namespace std;
int main(){
list<int> *l;
l[0].push_back(1);
l[10].push_back(12);
cout<<endl;
return 0;
}
Why are you using a pointer to a list? You didn't allocate memory for the list. You could use a container to store multiple lists, e.g. std:array for static number of elements or std::vector for dynamic number of elements:
#include <array>
#include <iostream>
#include <list>
#include <vector>
using std::array;
using std::vector;
using std::list;
using std::cout;
int main(){
std::array<list<int>, 11> l;
l[0].push_back(1);
l[10].push_back(12);
std::vector<list<int>> l2(11);
l2[0].push_back(1);
l2[10].push_back(12);
cout << '\n';
return 0;
}
list<int> *l; makes l a pointer to a list<int> but it doesn't actually create a list<int> - and definitely not an array of list<int> which you are trying to access.
Possible solutions.
Plain C fixed size arrays of list<int>:
#include <iostream>
#include <list>
int main() {
std::list<int> l[11]; // place for 11 list<int>`'s
l[0].push_back(1);
l[10].push_back(12);
}
Using the C++ fixed sized std::array:
#include <array>
#include <list>
int main() {
std::array<std::list<int>, 11> l; // place for 11 list<int>'s
l[0].push_back(1);
l[10].push_back(12);
}
Using a C++ std::vector that allows for dynamicially adding more list<int>'s:
#include <list>
#include <vector>
int main() {
std::vector<std::list<int>> l(11); // starts with place for 11 list<int>'s
l[0].push_back(1);
l[10].push_back(12);
}
list<int> *l; is a pointer to list, it is not initialized, so adding elements to it has undefined behaviour. Either you initialize it to a variable like:
list<int> l;
l.push_back(1);
l.push_back(12);
In this case you can only access the elements that already have data, l[0] or l[1].
Or you need to allocate space to the number of elements you need in your list.
For instance:
list<int> l[20];
l[0].push_back(1);
l[10].push_back(12);
In list<int> *l; is creating a pointer to a list. Before accessing l you need to assign valid address to it.
Something like this,
list<int> l;
list<int> *l2 = &l;
