godot/core/sort.h

/*************************************************************************/
/*  sort.h                                                               */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2017 Juan Linietsky, Ariel Manzur.                 */
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/*************************************************************************/
#ifndef SORT_H
#define SORT_H

#include "typedefs.h"
/**
	@author ,,, <red@lunatea>
*/

template<class T>
struct _DefaultComparator {

	inline bool operator()(const T&a,const T&b) const { return (a<b); }
};

template<class T, class Comparator=_DefaultComparator<T> >
class SortArray {

	enum {

		INTROSORT_TRESHOLD=16
	};

public:

	Comparator compare;


	inline const T& median_of_3(const T& a, const T& b, const T& c) const {

		if (compare(a, b))
			if (compare(b, c))
				return b;
			else if (compare(a, c))
				return c;
			else
				return a;
		else if (compare(a, c))
			return a;
		else if (compare(b, c))
			return c;
		else
			return b;
	}



	inline int bitlog(int n) const {
		int k;
		for (k = 0; n != 1; n >>= 1)
			++k;
		return k;
	}


	/* Heap / Heapsort functions */

	inline void push_heap(int p_first,int p_hole_idx,int p_top_index,T p_value,T* p_array) const {

		int parent = (p_hole_idx - 1) / 2;
		while (p_hole_idx > p_top_index && compare(p_array[p_first + parent], p_value)) {

			p_array[p_first + p_hole_idx] = p_array[p_first + parent];
			p_hole_idx = parent;
			parent = (p_hole_idx - 1) / 2;
		}
		p_array[p_first + p_hole_idx] = p_value;
	}

	inline void pop_heap(int p_first, int p_last, int p_result, T p_value, T* p_array) const {

		p_array[p_result]=p_array[p_first];
		adjust_heap(p_first,0,p_last-p_first,p_value,p_array);
	}
	inline void pop_heap(int p_first,int p_last,T* p_array) const {

	 	pop_heap(p_first,p_last-1,p_last-1,p_array[p_last-1],p_array);
	}

	inline void adjust_heap(int p_first,int p_hole_idx,int p_len,T p_value,T* p_array) const {


		int top_index = p_hole_idx;
		int second_child = 2 * p_hole_idx + 2;

		while (second_child < p_len) {

			if (compare(p_array[p_first + second_child],p_array[p_first + (second_child - 1)]))
				second_child--;

			p_array[p_first + p_hole_idx] = p_array[p_first + second_child];
			p_hole_idx = second_child;
			second_child = 2 * (second_child + 1);
		}

		if (second_child == p_len) {
			p_array[p_first + p_hole_idx] = p_array[p_first + (second_child - 1)];
			p_hole_idx = second_child - 1;
		}
		push_heap(p_first, p_hole_idx, top_index, p_value,p_array);
	}

	inline void sort_heap(int p_first,int p_last,T* p_array) const {

		while(p_last-p_first > 1) {

			pop_heap(p_first,p_last--,p_array);
		}
	}

	inline void make_heap(int p_first, int p_last,T* p_array) const {
		if (p_last - p_first < 2)
			return;
		int len = p_last - p_first;
		int parent = (len - 2)/2;

		while (true) {
			adjust_heap(p_first, parent, len, p_array[p_first + parent], p_array);
			if (parent == 0)
				return;
			parent--;
		}
	}

	inline void partial_sort(int p_first,int p_last,int p_middle,T* p_array) const {

		make_heap(p_first,p_middle,p_array);
		for(int i=p_middle;i<p_last;i++)
			if (compare( p_array[i],p_array[p_first]))
				pop_heap(p_first,p_middle,i,p_array[i],p_array);
		sort_heap(p_first,p_middle,p_array);
	}

	inline void partial_select(int p_first,int p_last,int p_middle,T* p_array) const {

		make_heap(p_first,p_middle,p_array);
		for(int i=p_middle;i<p_last;i++)
			if (compare( p_array[i],p_array[p_first]))
				pop_heap(p_first,p_middle,i,p_array[i],p_array);
	}

	inline int partitioner(int p_first, int p_last, T p_pivot, T* p_array) const {

		while (true) {
			while (compare(p_array[p_first],p_pivot))
				p_first++;
			p_last--;
			while (compare(p_pivot,p_array[p_last]))
				p_last--;

			if (!(p_first < p_last))
				return p_first;

			SWAP(p_array[p_first],p_array[p_last]);
			p_first++;
		}
	}

	inline void introsort(int p_first, int p_last, T* p_array, int p_max_depth) const {

		while( p_last - p_first > INTROSORT_TRESHOLD ) {

			if (p_max_depth == 0) {
				partial_sort(p_first,p_last,p_last,p_array);
				return;
			}

			p_max_depth--;

			int cut = partitioner(
				p_first,
				p_last,
				median_of_3(
					p_array[p_first],
					p_array[p_first + (p_last-p_first)/2],
					p_array[p_last-1]
				),
				p_array
			);

			introsort(cut,p_last,p_array,p_max_depth);
			p_last=cut;

		}
  	}

	inline void introselect(int p_first, int p_nth, int p_last, T* p_array, int p_max_depth) const {

		while( p_last - p_first > 3 ) {

			if (p_max_depth == 0) {
				partial_select(p_first,p_nth+1,p_last,p_array);
				SWAP(p_first,p_nth);
				return;
			}

			p_max_depth--;

			int cut = partitioner(
				p_first,
				p_last,
				median_of_3(
					p_array[p_first],
					p_array[p_first + (p_last-p_first)/2],
					p_array[p_last-1]
				),
				p_array
			);

			if (cut<=p_nth)
				p_first=cut;
			else
				p_last=cut;

		}

		insertion_sort(p_first,p_last,p_array);
	}

	inline void unguarded_linear_insert(int p_last,T p_value,T* p_array) const {

		int next = p_last-1;
		while (compare(p_value,p_array[next])) {
			p_array[p_last]=p_array[next];
			p_last = next;
			next--;
		}
		p_array[p_last] = p_value;
	}

	inline void linear_insert(int p_first,int p_last,T*p_array) const {

		T val = p_array[p_last];
		if (compare(val, p_array[p_first])) {

			for (int i=p_last; i>p_first; i--)
				p_array[i]=p_array[i-1];

			p_array[p_first] = val;
		} else
			unguarded_linear_insert(p_last, val, p_array);
	}

  	inline void insertion_sort(int p_first,int p_last,T* p_array) const {

		if (p_first==p_last)
			return;
		for (int i=p_first+1; i!=p_last ; i++)
			linear_insert(p_first,i,p_array);
	}

  	inline void unguarded_insertion_sort(int p_first,int p_last,T* p_array) const {

		for (int i=p_first; i!=p_last ; i++)
			unguarded_linear_insert(i,p_array[i],p_array);
	}

	inline void final_insertion_sort(int p_first,int p_last,T* p_array) const {

		if (p_last - p_first > INTROSORT_TRESHOLD) {
			insertion_sort(p_first,p_first+INTROSORT_TRESHOLD,p_array);
			unguarded_insertion_sort(p_first+INTROSORT_TRESHOLD,p_last,p_array);
		} else {

			insertion_sort(p_first,p_last,p_array);

		}
  	}

	inline void sort_range(int p_first, int p_last,T* p_array) const {

		if (p_first != p_last) {
			introsort(p_first, p_last,p_array,bitlog(p_last - p_first) * 2);
			final_insertion_sort(p_first, p_last, p_array);
		}
	}

	inline void sort(T* p_array,int p_len) const {

		sort_range(0,p_len,p_array);
	}

	inline void nth_element(int p_first,int p_last,int p_nth,T* p_array) const {

		if (p_first==p_last || p_nth==p_last)
			return;
		introselect(p_first,p_nth,p_last,p_array,bitlog(p_last - p_first) * 2);
	}

};




#endif