Question

i have a vector of vector “mydata”. i want to iterate my data in negative direction. the iterator should be started from the middle to the beginning.
i wish to use following way;

vector<vector<int> >::const_iterator points;
int i, k;

(lets assume k = 10)

for (i=k, points=mydata.begin()+k; i != -1; i--, points--){

     //do stuff
}

does this way is the proper way to iterate in backward? (I am using dev c++, so predicates and some modern commands cant be used.)
Hope your suggestions to do this.

Answer 1

Since it’s vector, you dont need to use iterator at all:

for (int k = 4; k >= 0; k--)
{
    // do something with v[k]
}

Example:

#include <iostream>
#include <vector>
using namespace std;

int main(int argc, char** argv)
{
    int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
    vector<int> v(arr, arr + 10);

    for (int k = 4; k >= 0; k--)
    {
        cout << v[k] << endl;
    }
}

output:

5
4
3
2
1