vector <vector<int> > v8;
int N;
cin >> N;
for (int i = 0; i < N; i  )
{
    int n;
    cin >> n;
    vector <int> temp;
    for (int i = 0; i < n; i  )
    {
        int x;
        cin >> x;
        temp.push_back(x);
    }
    v8.push_back(temp);
    
}

vector <int> ::iterator it;
for (it = v8.begin(); it < v8.end(); it  )
{
    cout << (*it) << " ";
}

I'm getting this error:

no operator "=" matches these operandsC/C  (349)
intro.cpp(161, 13): operand types are: __gnu_cxx::__normal_iterator<int *, std::vector<int, std::allocator<int>>> = __gnu_cxx::__normal_iterator<std::vector<int, std::allocator<int>> *, std::vector<std::vector<int, std::allocator<int>>, std::allocator<std::vector<int, std::allocator<int>>>>>

How should I solve this??

CodePudding user response：

The problem is that it is an iterator to 1D vector<int> while b8.begin() gives us an iterator to a 2D vector<vector<int>>. So these iterators are not compatible with each other. That is, you cannot use the iterator it to traverse a 2D vector.

You can solve this by changing vector <int> ::iterator it; as shown below:

    vector <vector<int>> ::iterator it;   //change made here. Now it is an iterator to a 2D vector
    for (it = v8.begin(); it != v8.end(); it  )  
    {
        
        for(auto i = (*it).begin(); i != (*it).end();  i) // i is an iterator to a 1D vector
        {
            cout << (*i) << " ";//it changed to i
        }
        
    }

Another option would be to use auto with range-based for loop as shown below:

for (auto &row: v8)
{
    for(auto &col: row)
    {
        cout << col << " ";
    }
      
}

CodePudding user response：

To iterate through vectors in v8, enumerating their elements, use range-based for loops.

for (auto& v: v8) {
    for (auto& it: v) {
        std::cout << it << ' ';
    }
}