How do I access second element of a pair nested in another pair in stl?

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I have a vector like this :
vector < pair < int, pair < int,int > > > v
I want to access all the three elements . How can i do that through iterator?

What I have tried:

I looked for the possible answers on the internet but cannot get any satisfactory answer. I tried iterator like this :
vector < pair < int,pair <int,int> > > v;
vector < pair < int,pair <int,int> > > :: iterator it=v.begin();
cout<<it->first->second;
Its not working

Posted 6-Jul-16 0:49am

Member 12621273

Updated 9-Jun-21 13:39pm

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CPallini 6-Jul-16 7:01am

As far as I know your declaration of v is not valid.

Member 12621273 6-Jul-16 7:06am

i have corrected it now

Philippe Mori 6-Jul-16 15:17pm

Obviously, since the second pair is a value, last arrow should be replaced by a dot.

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Richard MacCutchan · Answer 1 · 2016-07-06T01:11:00

A vector only accepts one Type in its implementation, so you cannot have <int, pair>. You need to create a new class, or use a pair that also contains a pair; something like:

C++

vector<pair<int, pair<int, int > > > v;
pair<int, int> p;
pair<int, pair< int, int> > q;
p.first = 1;
p.second = 2;
q.first = 1;
q.second = p;
v.push_back(q);

p.first = 3;
p.second = 4;
q.first = 2;
q.second = p;
v.push_back(q);
for (vector<pair<int, pair<int, int > > >::iterator it = v.begin(); it < v.end(); ++it)
{
    q = *it;
    int num = q.first;
    p = q.second;
    cout << num << " : " << p.first << " - " << p.second << endl;
}

Member 15239417 · Answer 2 · 2021-06-09T09:09:00

Solution 3

you do like this,
vector <pair <int,="" pair="" int=""> > > v;
INSERION OF VALUES:
v.push_back(make_pair(a, make_pair(b, c)));
ACCESSING VALUES:
a = v[i].first;
b = v[i].second.first;
c = v[i].second.second;

Posted 9-Jun-21 9:09am

Member 15239417

Updated 9-Jun-21 9:56am

merano99 · Answer 3 · 2021-06-09T13:39:00

C++

// I have a vector like this :
vector < pair < int, pair < int, int > > > v;
//	I want to access all the three elements.How can i do that through iterator ?

pair < int, int > p1(1,2);
pair < int, pair < int, int > > p2(3, p1);

v.push_back(p2);

for (auto it : v) {
	cout << ">" << "; " << it.first << "; " << it.second.first << "; " << it.second.second << "\n";
	}

How do I access second element of a pair nested in another pair in stl?

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