fork download 
  1. #include <iostream>
  2. #include <algorithm>
  3. #include <map>
  4. using namespace std;
  5.  
  6. template<typename Map, typename K>
  7. auto tolerant_find(const Map & map, const K & lookup, const K & tolerance) -> decltype(map.begin()) {
  8.     // Assuming (first,last) is a sorted sequence of pairs
  9.  
  10.     // First, find sub-sequence of keys "near" the lookup value
  11.     auto first = map.lower_bound(lookup - tolerance);
  12.     auto last = map.upper_bound(lookup + tolerance);
  13.  
  14.     // If they are equal, the sequence is empty, and thus no entry was found.
  15.     // Return the end iterator to be consistent with std::find.
  16.     if (first == last) {
  17.     	return map.end();
  18.     }
  19.  
  20.     // Then, find the one with the minimum distance to the actual lookup value
  21.     typedef typename Map::mapped_type T;
  22.     return std::min_element(first, last, [lookup](std::pair<K,T> a, std::pair<K,T> b) {
  23.         return std::abs(a.first - lookup) < std::abs(b.first - lookup);
  24.     });
  25. }
  26.  
  27. int main() {
  28. 	std::map<float,int> mymap = {
  29. 		{ 1.0, 1 },
  30. 		{ 5.0, 2 },
  31. 		{ 5.1, 3 },
  32. 		{ 5.11, 4 },
  33. 		{ 5.2, 5 }
  34. 	};
  35.  
  36. 	// This should find the key 5.11
  37. 	cout << tolerant_find(mymap, 5.15, 0.1)->first << endl;
  38. 	// This should find the key 5.2
  39. 	cout << tolerant_find(mymap, 5.16, 0.1)->first << endl;
  40.  
  41. 	// This should print "not found".
  42. 	cout << (tolerant_find(mymap, 2.0, 0.1) == mymap.end() ? "not found" : "found") << endl;
  43.  
  44. 	return 0;
  45. }
Success #stdin #stdout 0s 3432KB
comments (?)
stdin 
Standard input is empty
stdout 
5.11
5.2
not found
https://ideone.com/qT3JIa
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!