C/C++ How to Properly Resize and Populate a Vector in C++ Without Using push_back?

[EvanET]

Resize vector countDown to have newSize elements. Populate the vector with integers {newSize, newSize - 1, ..., 1}. Ex: If newSize = 3, then countDown = {3, 2, 1}, and the sample program outputs:

3 2 1 Go!

**I want to do this WITHOUT push_back**
#include <iostream>
#include <vector>
using namespace std;

int main() {
vector<int> countDown(0);
int newSize = 0;
int i = 0;

newSize = 3;

//enter code here

for (i = 0; i < newSize; ++i) {
cout << countDown.at(i) << " ";
}
cout << "Go!" << endl;

return 0;
}

 

[I like Serena]

Resize vector countDown to have newSize elements. Populate the vector with integers {newSize, newSize - 1, ..., 1}. Ex: If newSize = 3, then countDown = {3, 2, 1}, and the sample program outputs:

3 2 1 Go!

**I want to do this WITHOUT push_back**
#include <iostream>
#include <vector>
using namespace std;

int main() {
vector<int> countDown(0);
int newSize = 0;
int i = 0;

newSize = 3;

//enter code here

for (i = 0; i < newSize; ++i) {
cout << countDown.at(i) << " ";
}
cout << "Go!" << endl;

return 0;
}

Hi EvanET! Welcome to MHB! ;)

To pre-allocate the required memory, we can use 2 methods:
1. Call [M]countDown.resize(newSize)[/M].
2. Re-create the vector by executing [M]countDown = vector<int>(newSize)[/M].

After that we still have to fill in the newly available memory locations.