actually, I am new to C++ , although not new to programming. i have a vector of pairs ,

```
vector<pair<double, pair<int,int> >>
```

and i want to sort it in incresing order. for simplicity, i am using sort() inbulit function. does pair has ibuilt '<' operator ? or we have to override it ? if yes, then how will cmp will be declared ?

x,y are coordinates of a point and double is their polar angle. and i am doing this sorting so that after sorting the points are in the order which will make a polygon. thanks if u can help me. any help will be appreciated.