push_back到向量时的运行时错误

Question

#include <iostream>
#include <utility>
#include <vector>
using namespace std;

int main() {
    vector<pair<int, int>*> *v;
    pair<int, int> *x = new pair<int, int>();
    cin >> x->first >> x->second;
    v->push_back(x);
    cout << v->size() << endl;
    return 0;
}

Why does this code get run-time error? I dont understand. All I do is appending a pair pointer to a vector of pair pointer.

Answer 1

First of all: Vector definition should be (this resolves the run-time error):

vector<pair<int, int>*> v;

Second, you don't release the memory of the new pair. This will solve that issue too:

vector<pair<int, int>> v;
pair<int, int> x{ 0,0 };

A vector of pairs, rather than a vector of pair-pointers. On the other hand: If it necessary to use a vector of pointers, smart pointers is a better choice.