Question

I don’t know what’s wrong with the follwing code, it should read numbers and put their value with the position together in a vector of pairs and then sort them and print out the positions. I removed the part with sort – i thought the problem was there, but i received an error on compilation again.

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

int main(void)
{
        unsigned int n,d,a[65],b[65],s,i,j,t,us=0;
        pair<unsigned int,unsigned int> temp;
        vector< pair<unsigned int,unsigned int> > v;
        cin >> n;
        for(i=0;i<n;i++)
        {
                cin >> t;
                temp(t, i+1);
                v.push_back(temp);
        }
        cin >> d;
        for(i=0;i<d;i++) cin >> a[i] >> b[i];
        for(i=0;i<v.size();i++)
        {
                cout << v[i].first << " -- " << v[i].second << endl;
        }
        return 0;
}

Please tell me where is the problem. Thanks.

Answer 1

The problem is temp(t, i+1);

You need to set the first and second manually

temp.first = t;
temp.second = i + 1;

Alternatively you can declare temp inside the loop (probably what I’d do).

for(i=0;i<n;i++) 
{ 
    cin >> t; 
    pair<unsigned int,unsigned int> temp(t, i+1); 
    v.push_back(temp); 
} 

Or a second alternate, use the make_pair helper function, and do away with temp completely (thanks to KennyTM for the reminder)

for(i=0;i<n;i++) 
{ 
    cin >> t; 
    v.push_back(make_pair(t, i+1)); 
} 

Hope this helps