Question

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How do I sort a vector of pairs based on the second element of the pair?

I have a vector of this type: vector< pair<float, int> > vect; I want sort its elements according to the descending order of the floats values (the first value of pairs).
For example vect = [<8.6, 4>, <5.2, 9>, <7.1, 23>], after sorting I want to have: [<5.2, 9>, <7.1, 23>, <8.6, 4>]
how can I simply do that in C++ ?

Answer 1

struct cmp_by_first {
  template<typename T>
  bool operator<(const T& x, const T& y) const { return x.first < y.first; }
};

std::sort(vect.begin(), vect.end(), cmp_by_first());