位圖排序

利用位圖對數據進行排序。

前提：待排數據不能有重複，且要能估計出待排數據值的上界（越精確效率越高）

時間複雜度：設待排數據值上界爲M，待排數據量爲N，則時間複雜度爲O（2M+N）

c++實現代碼：

#ifndef BITMAP_SORT_H
#define	BITMAP_SORT_H

//sort the array by bitmap, it demand all elements of src can't be repeated.
const int WORD = 32;
const int SHIFT = 5;  //left shift 5 bits equal to mutiply 32
const int MASK = 0x1f;//31,M%N: if N%2=0, M%N = M&(N-1)
const int MAX_VALUE = 10000000;  //The maximum value of all elements of src.
int bitmap[MAX_VALUE/WORD+1];    //The array of bitmap.

//set the bit
void set(int i)
{
	bitmap[i>>SHIFT] |= (1<<(i&MASK));
}

//clear the bit
void clear(int i)
{
	bitmap[i>>SHIFT] &= ~(1<<(i&MASK));
}

//return the result of the bit
int test(int i)
{
	return (bitmap[i>>SHIFT] & (1<<(i&MASK)));
}

void bitmap_sort(int src[], int size)
{
	int i;
	for (i=0; i<MAX_VALUE; ++i)
	{
		clear(i);
	}
	for (i=0; i<size; ++i)
	{
		set(src[i]);
	}
	int j=0;
	for (i=0; i<MAX_VALUE; ++i)
	{
		if (test(i))
		{
			src[j++] = i;
		}
	}
}

#endif