How do I sort a vector<int> which is an element of a 2-d matrix?

Question

I am trying to use STl sort on a vector which is a part of a 2d array, but getting an error. What is the correct way to do this? Trying to use vector normally as sort(A,A+A.size()) where A is the vector.

I have added a comment at the sort statement that is giving an error.

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

int main()
{
    while(1)
    {
        int m,n;
        cin>>m>>n;

        int arr[m][n];
        for(int x=0;x<m;x++)
        for(int y=0;y<n;y++)
        cin>>arr[x][y];

        vector<int> cost[m][n]; //THIS IS THE 2-D ARRAY OF VECTORS

        cost[0][0].push_back(arr[0][0]);

        for(int i=1;i<m;i++)
        {
           cost[0][i].push_back(cost[0][i-1][0]+arr[0][i]);
        }
        for(int i=1;i<n;i++)
        {
           cost[i][0].push_back(cost[i-1][0][0]+arr[i][0]);
        }

        for(int i=1;i<m;i++)
        {
                for(int j=1;j<n;j++)
                {
                        vector<int>::iterator it;
                        for(it=cost[i-1][j].begin(); it!=cost[i-1][j].end();it++)
                        cost[i][j].push_back(((*it)+arr[i][j]));

                        vector<int>::iterator it1;
                        for(it1=cost[i][j-1].begin(); it1!=cost[i][j-1].end();it1++)
                        cost[i][j].push_back(((*it1)+arr[i][j]));

                        //freevec(cost[i][j]);
                }
        }

        int tx,ty,k;
        cin>>tx>>ty>>k;


//THIS STEP IS GIVING AN ERROR. 
            sort(cost[tx][ty],cost[tx][ty]+cost[tx][ty].size()); 
//THIS STEP IS GIVING AN ERROR. 


        cout<<cost[tx][ty][k-1]<<endl;




           /*             
        for(int i=0;i<m;i++)
        {
                for(int j=0;j<n;j++)
                {       cout<<"\n\n"<<arr[i][j]<<endl;
                        vector<int>::iterator it;
                        for(it=cost[i][j].begin(); it!=cost[i][j].end();it++)
                        cout<<(*it)<<" ";
                }
                cout<<endl;
        }*/

   }
}

Answer 1

A vector doesn't change its properties by being an element of an array. So you would sort it just like you would sort a vector that is not an element of a 2D array:

sort(cost[tx][ty].begin(), cost[tx][ty].end());

or

sort(begin(cost[tx][ty]), end(cost[tx][ty]));

Assuming argument dependent lookup finds std::sort, std::begin and std::end.