Example for the use of map::lower_bound and map::upper_bound in a map of pairs

maprange.cpp

#include <iostream>
#include <utility>
#include <limits>
#include <map>

using mymap = std::map<std::pair<int, int>, int>;

std::ptrdiff_t num_per_node(const mymap &map, const int node_id)
{
  using std::distance;
  static constexpr int min = std::numeric_limits<int>::min();
  static constexpr int max = std::numeric_limits<int>::max();

  auto lo = map.lower_bound({node_id,min});
  auto hi = map.upper_bound({node_id,max});
  return distance(lo,hi);
}

int main() {
  mymap m
  { {{1,3},1} , {{3,4},2} , {{3,5},3} , {{3,9},4} , {{4,2},5} , {{4,3},6} , {{5,1},7} , {{8,2},8} };

  for (int node_id = 0 ; node_id < 10 ; ++node_id)
    std::cout << "node-id " << node_id << ": " << num_per_node(m,node_id) << '\n';

  return 0;
}