c++ - Vector converted all negative values to zero

Question

I made a vector of constant size to store negative values, and then printing the values all I got was zeroes. I just want to know why it is not storing negative values.

#include <iostream>
#include <vector>

int main() {
    std::vector<int> v(5);
    v.push_back(-1);
    v.push_back(-2);
    v.push_back(-3);
    v.push_back(-4);
    v.push_back(-5);

    for (int i=0; i<5; i++)
       std::cout << v[i] << " ";  // All I got was zeroes
}

Answer 1

That's because push_back puts new elements onto the end of the vector.

You can see the effect by running i to 9: the negative numbers will occupy v[5] to v[9].

Writing

std::vector<int> v{-1, -2, -3, -4, -5};

instead is a particularly elegant fix.