Created
December 20, 2017 14:04
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template<typename T> │ | |
void merge(T begin, T end, T mid, T scratch_space){ │ | |
│ | |
auto first{begin}; │ | |
auto second{mid}; │ | |
auto write{scratch_space}; │ | |
│ | |
// Alternate between subarrays to create sorted │ | |
// sequence in the scratch space │ | |
for(int i{0};i<std::distance(begin,end);++i){ │ | |
if(first == mid){ │ | |
*write++ = *second++; │ | |
} │ | |
else if(second == end){ │ | |
*write++ = *first++; │ | |
} │ | |
else{ │ | |
auto& source = (*first < *second) ? first : second; │ | |
*write++ = *source++; │ | |
} │ | |
} │ | |
│ | |
// Copy the contents of the scratch space back │ | |
std::copy(scratch_space, write, begin); │ | |
} │ | |
│ | |
template<typename T> │ | |
void merge_sort(T begin, T end, T scratch_space){ │ | |
│ | |
size_t length = std::distance(begin, end); │ | |
│ | |
if(length == 1){ │ | |
return; │ | |
} │ | |
│ | |
auto mid = begin+(length/2); │ | |
merge_sort(begin, mid, scratch_space); │ | |
merge_sort(mid, end, scratch_space); │ | |
│ | |
merge(begin, end, mid, scratch_space); │ | |
} |
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