[cpp][12_sorts] inplace_merge_sort, done.

Author: Liam0205

c-cpp/12_sorts/merge_sort.hpp

@@ -47,5 +47,16 @@ void merge_sort(FrwdIt first, FrwdIt last, BinaryPred comp = BinaryPred()) {
  std::copy(tmp.begin(), tmp.end(), first);
 }
 
+template <typename BidirIt,
+ typename BinaryPred = std::less<typename std::iterator_traits<BidirIt>::value_type>>
+void inplace_merge_sort(BidirIt first, BidirIt last, BinaryPred comp = BinaryPred()) {
+ const auto len = std::distance(first, last);
+ if (len <= 1) { return; }
+ auto cut = first + len / 2;
+ merge_sort(first, cut, comp);
+ merge_sort(cut, last, comp);
+ std::inplace_merge(first, cut, last, comp);
+}
+
 #endif // SORTS_MERGE_SORT_HPP_
 

c-cpp/12_sorts/merge_sort_test.cc

@@ -7,9 +7,18 @@
 #include "merge_sort.hpp"
 
 int main() {
- std::vector<int> test_data{0, -1, 3, 190, -500};
- merge_sort(test_data.begin(), test_data.end());
- for (auto i : test_data) {
+ const std::vector<int> test_data{0, -1, 3, 190, -500};
+
+ std::vector<int> a{test_data};
+ merge_sort(a.begin(), a.end());
+ for (auto i : a) {
+ std::cout << i << ' ';
+ }
+ std::cout << std::endl;
+
+ std::vector<int> b{test_data};
+ inplace_merge_sort(b.begin(), b.end());
+ for (auto i : b) {
  std::cout << i << ' ';
  }
  std::cout << std::endl;