Bitwise mask and manipulation...
Hi all, Im trying to learn radix sorting here. I found this nice sample code. While trying to undestand the code i have a few doubts.
Can you explain what the coder has done?
Code:
#include <iostream.h>
#include <stdlib.h>
#include <string.h>
void radix (int byte, long N, long *source, long *dest)
{
long count[256];
long index[256];
memset (count, 0, sizeof (count));
for ( int i=0; i<N; i++ ) count[((source[i])>>(byte*8))&0xff]++;
index[0]=0;
for ( i=1; i<256; i++ ) index[i]=index[i-1]+count[i-1];
for ( i=0; i<N; i++ ) dest[index[((source[i])>>(byte*8))&0xff]++] = source[i]; // Doubt 1.
}
void radixsort (long *source, long *temp, long N)
{
radix (0, N, source, temp);
radix (1, N, temp, source);
radix (2, N, source, temp);
radix (3, N, temp, source);
}
void make_random (long *data, long N)
{
for ( int i=0; i<N; i++ ) data[i]=rand()|(rand()<<16);
}
long data[100];
long temp[100];
void main (void)
{
make_random(data, 100);
radixsort (data, temp, 100);
for ( int i=0; i<100; i++ ) cout << data[i] << '\n';
}
In function radix i have marked the dount. Can you explain why the coder has used this sentence"?
for ( i=0; i<N; i++ )
{
dest[index[((source[i])>>(byte*8))&0xff]++] = source[i];
}
in particular - whats right shift operator doing and why is & doing here .. which is incremented here?
would help me understand it better
thank
regards
KR
