Segmentation Fault in C++ - Vectors

Question

#include <cmath>
#include <cstdio>
#include <string>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() 
{
    int a, b;
    cin>>a;
    vector<int> numbers;
    for(int i=0; i<a; i++)
    {
        cin>>b;
        numbers.push_back(b);
    }

    int c,d,e;
    cin>>c;
    numbers.erase(numbers.begin()+c-1);
    cin>>d>>e;
    numbers.erase(numbers.begin()+d-1, numbers.end()+e);

    cout<<numbers.size();
    for(int x : numbers)
        cout<<x<<" ";

    return 0;
}

Hello everyone, I am learning c++ and writing a very simple program, but this code is giving "Segmentation Fault" as error. I really could not figure out why this is happening.

Thank you.

Answer 1

This line

numbers.erase(numbers.begin()+d-1, numbers.end()+e);

cannot be correct. Incrementing the end iterator never gets you a valid iterator. It is not quite clear what you want to do, but if you want to erase elements in the range of indices [d,e) then that would be

numbers.erase(numbers.begin()+d, numbers.begin()+e);

Note: No +1 needed on the first, because the first is inclusive. And you get an iterator to the e-th element by incrementing the begin iterator not the end iterator (well... I assume the common 0-based counting, ie the "first" element is the 0th element ;).

Also, as mentioned in comments, you should check if the user entered values are in range, before calling erase. erase does no bounds-checking. If you pass invalid iterators your get undefined behavior.