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  1. #include <iostream>
  2. #include <iterator>
  3. #include <algorithm>
  4. #include <vector>
  5. #include <queue>
  6. #include <cassert>
  7.  
  8.  
  9. template<typename Iterator, typename Operation>
  10. void iterate_ranges (Iterator from, Iterator to, Operation op) {
  11.   using R = typename std::iterator_traits<Iterator>::value_type;
  12.   using N = typename std::decay<decltype(std::declval<R>().first)>::type;
  13.   using P = std::pair<N, R>;
  14.   auto compare = [](P const & left, P const & right) {
  15.     return left.first > right.first;};
  16.  
  17.   std::priority_queue<P, std::vector<P>, decltype(compare)> queue(compare);
  18.  
  19.   auto push = [& queue] (P p) {
  20.     if (p.first < p.second.last) queue.push(p); };
  21.   auto next = [](P const & p) -> P {
  22.     assert(p.second.step > 0);
  23.     return {p.first + p.second.step, p.second}; };
  24.   auto init = [&push] (R const & r) {
  25.     push({r.first, r}); };
  26.  
  27.   std::for_each(from, to, init);
  28.  
  29.   if (queue.empty()) return;
  30.  
  31.   N last = queue.top().first;
  32.   push(next(queue.top()));
  33.   queue.pop();
  34.   op(last);
  35.  
  36.   while (! queue.empty()) {
  37.     P current = queue.top();
  38.     queue.pop();
  39.     if (current.first != last) {
  40.       op(current.first);
  41.       last = current.first;
  42.     }
  43.     push(next(current));
  44.   }
  45. }
  46.  
  47. struct Range {
  48.   int first;
  49.   int last;
  50.   int step;
  51. };
  52.  
  53.  
  54. int main() {
  55.   Range ranges [] = {
  56.     {1, 10, 2},
  57.     {2, 50, 5}};
  58.  
  59.   auto print = [](auto n) { std::cout << n << std::endl; };
  60.  
  61.   iterate_ranges(std::begin(ranges), std::end(ranges), print);
  62. }
Success #stdin #stdout 0s 15240KB
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https://ideone.com/kqUFEy
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
secret

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