bsnes-libretro/nall/sort.hpp
Tim Allen 0b923489dd Update to 20160106 OS X Preview for Developers release.
byuu says:

New update. Most of the work today went into eliminating hiro::Image
from all objects in all ports, replacing with nall::image. That took an
eternity.

Changelog:
- fixed crashing bug when loading games [thanks endrift!!]
- toggling "show status bar" option adjusts window geometry (not
  supposed to recenter the window, though)
- button sizes improved; icon-only button icons no longer being cut off
2016-01-07 19:17:15 +11:00

75 lines
2.0 KiB
C++

#pragma once
#include <algorithm>
#include <nall/utility.hpp>
//class: merge sort
//average: O(n log n)
//worst: O(n log n)
//memory: O(n)
//stack: O(log n)
//stable?: yes
//note: merge sort was chosen over quick sort, because:
//* it is a stable sort
//* it lacks O(n^2) worst-case overhead
#define NALL_SORT_INSERTION
//#define NALL_SORT_SELECTION
namespace nall {
template<typename T, typename Comparator> auto sort(T list[], unsigned size, const Comparator& lessthan) -> void {
if(size <= 1) return; //nothing to sort
//use insertion sort to quickly sort smaller blocks
if(size < 64) {
#if defined(NALL_SORT_INSERTION)
for(signed i = 1, j; i < size; i++) {
T copy = std::move(list[i]);
for(j = i - 1; j >= 0; j--) {
if(!lessthan(copy, list[j])) break;
list[j + 1] = std::move(list[j]);
}
list[j + 1] = std::move(copy);
}
#elif defined(NALL_SORT_SELECTION)
for(unsigned i = 0; i < size; i++) {
unsigned min = i;
for(unsigned j = i + 1; j < size; j++) {
if(lessthan(list[j], list[min])) min = j;
}
if(min != i) std::swap(list[i], list[min]);
}
#endif
return;
}
//split list in half and recursively sort both
unsigned middle = size / 2;
sort(list, middle, lessthan);
sort(list + middle, size - middle, lessthan);
//left and right are sorted here; perform merge sort
T* buffer = new T[size];
unsigned offset = 0, left = 0, right = middle;
while(left < middle && right < size) {
if(!lessthan(list[right], list[left])) {
buffer[offset++] = std::move(list[left++]);
} else {
buffer[offset++] = std::move(list[right++]);
}
}
while(left < middle) buffer[offset++] = std::move(list[left++]);
while(right < size) buffer[offset++] = std::move(list[right++]);
for(unsigned i = 0; i < size; i++) list[i] = std::move(buffer[i]);
delete[] buffer;
}
template<typename T> auto sort(T list[], unsigned size) -> void {
return sort(list, size, [](const T& l, const T& r) { return l < r; });
}
}