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  1.     #include <map>
  2.     #include <vector>
  3.     #include <iostream>
  4.     #include <algorithm>
  5.     using namespace std;
  6.  
  7.     const int N = 1e4 + 1;
  8.     vector<int> v(N);
  9.     vector<int> sorted(N);
  10.     map<int, int> counts;
  11.     long long start;
  12.  
  13.     void startClock() {
  14.         start = clock();
  15.     }
  16.  
  17.     void stopClock() {
  18.         cout << float( clock () - start ) /  CLOCKS_PER_SEC << endl;
  19.     }
  20.  
  21.     void copyOriginal() {
  22.         for (int i = 0; i < N; ++i)
  23.             sorted[i] = v[i];
  24.     }
  25.  
  26.     void sortWLambda(map<int, int>& counts) {
  27.         cout << "sorting with lambda" << endl;
  28.         sort(sorted.begin(), sorted.end(), [&counts](const int& a, const int& b) {
  29.             if (*counts.find(a) != *counts.find(b)) return *counts.find(a) < *counts.find(b);
  30.             return a < b;
  31.         });
  32.     }
  33.  
  34.     bool comparator(const int& a, const int& b) {
  35.         if (*counts.find(a) != *counts.find(b)) return *counts.find(a) < *counts.find(b);
  36.         return a < b;
  37.     }
  38.  
  39.     void sortWoLambda() {
  40.         cout << "sorting w/o lambda" << endl;
  41.         sort(sorted.begin(), sorted.end(), comparator);
  42.     }
  43.  
  44.     int main() {
  45.         for (int i = 0; i < N; ++i) {
  46.             int num = rand() % 1234;
  47.             counts[num]++;
  48.             v[i] = num;
  49.         }
  50.  
  51.         copyOriginal();
  52.         startClock();
  53.         sortWLambda(counts);
  54.         stopClock();
  55.  
  56.         copyOriginal();
  57.         startClock();
  58.         sortWoLambda();
  59.         stopClock();
  60.  
  61.         return 0;
  62.     }
Success #stdin #stdout 0.03s 16072KB
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Standard input is empty
stdout
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sorting with lambda
0.019469
sorting w/o lambda
0.014591
https://ideone.com/9nS4aw
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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