CODEWITHSUNDEEP
c++templatesdictionaryvectorstl
user1905552
user1905552

Reputation: 101

Transfer contents of map to a single vector of custom data structure

When I try to execute a program that calls my method I get a segmentation fault (core dumped) but I just cannot see the error. Have I made some kind of noob mistake? 

#include<map>
#include<vector>
//#include<iostream>
//#include<algorithm>
using namespace std;

template <class T>
class Record{
   public:
      T item;
      int total;
};

template <class T>
class Counter{
   public:
      map<T, int> m;

void printSummary(){

      typename map<T, int>::const_iterator itr; 
      vector< Record<T> > printlist;
      int i = 0;

      for( itr = m.begin(); itr != m.end(); ++itr ){
         printlist[i].item = (*itr).first;
         printlist[i].total = (*itr).second;
         i++;
      }

Upvotes: 0

Views: 66

Answers (2)

Thomas
Thomas

Reputation: 2163

You can access 

printlist[i]

only if the vector has enough elements. You could use another map to get a container with random access.

Upvotes: 0

hmjd
hmjd

Reputation: 121961

printlist is an empty vector when the following lines are executed:

printlist[i].item = (*itr).first;
printlist[i].total = (*itr).second;

which results in out of bounds access, causing undefined behaviour and in this case a segmentation fault. Either use push_back() or create the vector with the required number of elements and leave the for loop as is:

vector< Record<T> > printlist(m.size());

Upvotes: 1

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