Assigning to a two dimensional vector in c++ - c++

Question

#include<bits/stdc++.h>
using namespace std;
main()
{
vector<vector<int> > v;
for(int i = 0;i < 3;i++)
{
vector<int> temp;
for(int j = 0;j < 3;j++)
{
temp.push_back(j);
}
//cout<<typeid(temp).name()<<endl;
v[i].push_back(temp);
}
}
I am trying to assign to a two dimensional vector. I am getting the following error
No matching function for call to
std ::vector<int>::push_back(std::vector<int> &)

Answer 1

Problem: Your vector v is empty yet and you can't access v[i] without pushing any vector in v.
Solution: Replace the statement v[i].push_back(temp); with v.push_back(temp);

Answer 2

You can follow this process :
#include<bits/stdc++.h>
using namespace std;
int main()
{
vector<vector<int> > v;
for(int i = 0;i < 3;i++)
{
vector<int> temp;
for(int j = 0;j < 3;j++)
{
temp.push_back(j);
}
//cout<<typeid(temp).name()<<endl;
v.push_back(temp);
}
for(int i = 0; i < 3; i++){
for(int j = 0; j < 3; j++){
cout << v[i][j] << " ";
}
cout << endl;
}
}

Answer 3

v[0] is empty, you should use v.push_back(temp);
You could use at approach to avoid this error:
for(int i = 0; i < 3; i++){
vector <vector <int> > v;
vector <int> temp;
v.push_back(temp);
v.at(COLUMN).push_back(i);
}
Then you could access it through:
v.at(COLUMN).at(ROWS) = value;

Answer 4

v[i].push_back(temp);
should be
v.push_back(temp);
v is type of std::vector<vector<int>>, v[i] is type of std::vector<int>

Answer 5

You should use v instead of v[i]. (C++11)
#include <iostream>
#include <vector>
using namespace std;
int main(int argc, char* argv[])
{
vector<vector<int> > v;
for(int i = 0;i < 3;i++)
{
vector<int> temp;
for(int j = 0;j < 3;j++)
{
temp.push_back(j);
}
v.push_back(temp);
}
for (auto element: v) {
for (auto atom: element) {
cout << atom << " ";
}
cout << "\n";
}
return 0;
}

Answer 6

Think of it this way: "How do I insert a variable temp of type T into my vector of std::vector<T>?" In your case it is:
v.push_back(temp);
T itself being a vector doesn't make a difference. Then to print out your vector (of vectors) you can use two for loops:
for (std::size_t i = 0; i < v.size(); i++){
for (std::size_t j = 0; j < v[i].size(); j++){
std::cout << v[i][j] << ' ';
}
std::cout << std::endl;
}

Answer 7

Just do it...
#include<bits/stdc++.h>
using namespace std;
int main()
{
vector<vector<int> > v;
for(int i = 0; i < 3; i++)
{
vector<int> temp;
for(int j = 0; j < 3; j++)
{
temp.push_back(j);
}
v.push_back(temp);//use v instead of v[i];
}
}