Iterator printing from vector unneeded values - c++

Question

The intended nature of the program is to randomly generate numbers into a vector container, then sort them in ascending order and print the numbers out. The program compiles correctly but also sorts and prints the value 0 for each number that is generated.
#include "stdafx.h"
//contains all header files (ctime, algorithm, iostream, vector), also
defines const vector size as 250
using namespace std;
void genRndNums(vector <int> &v);
void printVec(vector <int> &v);
int main()
{
vector <int> myVector(VEC_SIZE);
genRndNums(myVector);
printVec(myVector);
return 0;
}
void genRndNums(vector <int> &v)
{
int v1;
srand(time(nullptr));
for (int i = 0; i < VEC_SIZE; i++)
{
v1 = rand() % 1000 + 1;
v.push_back(v1);
//v.push_back(rand() % 1000 + 1);
}
}
void printVec(vector <int> &v)
{
vector<int>::iterator it;
sort(v.begin(), v.end());
for (it = v.begin(); it != v.end(); it++)
{
cout << *it << " ";
}
}
In the case that 250 numbers were printed out, it would display the integer 0 250 times and then display the rest of the numbers in ascending sequence.
This is due to the for-loop in the print function having something misplaced, but I am not sure how to get the vector to display only the randomized integers.

Answer 1

Since you are using push_back to add elements to the vector, you need to start with an empty vector. I.e. you need to replace vector <int> myVector(VEC_SIZE); with vector <int> myVector;.

Answer 2

This is a common mistake. push_back adds to the end of the vector whose size is already VEC_SIZE. You can start with an empty vector like this:
vector <int> myVector;
or you can assign values to existing vector (whose size is VEC_SIZE) elements like this:
for (int i = 0; i < VEC_SIZE; i++)
{
v1 = rand() % 1000 + 1;
v[i] = v1;
}

Answer 3

Your vector constructor creates vector with 250 numbers (each with 0 value). To that numbers you appends another 250 generated numbers.
You shall not create that 250 numbers at the beginning
#include <vector>
#include <algorithm>
#include <random>
#include <iostream>
int main()
{
std::vector<int> v;
{
std::random_device r;
std::default_random_engine e(r());
std::uniform_int_distribution<int> d(1, 6);
std::generate_n(std::back_inserter(v), 250, [&](){ return d(r); });
}
std::sort(v.begin(), v.end());
for (auto x : v) {
std::cout << x << "\n";
}
return 0;
}
or override them
#include <vector>
#include <algorithm>
#include <random>
#include <iostream>
int main()
{
std::vector<int> v(250);
{
std::random_device r;
std::default_random_engine e(r());
std::uniform_int_distribution<int> d(1, 6);
std::generate(v.begin(), v.end(), [&](){ return d(r); });
}
std::sort(v.begin(), v.end());
for (auto x : v) {
std::cout << x << "\n";
}
return 0;
}