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| 1 | +#ifndef ALGO_RADIX_SORT_H__ |
| 2 | +#define ALGO_RADIX_SORT_H__ |
| 3 | + |
| 4 | +#include <stdint.h> |
| 5 | +#include <string.h> |
| 6 | +#include <stdlib.h> |
| 7 | +#include <assert.h> |
| 8 | +#include <generic.h> |
| 9 | +#include <memory> |
| 10 | + |
| 11 | +namespace alg { |
| 12 | + /** |
| 13 | + * couting sort |
| 14 | + */ |
| 15 | + static void radix_(int byte, const unsigned N, const uint32_t *source, uint32_t *dest) { |
| 16 | + unsigned count[256]; |
| 17 | + unsigned index[256]; |
| 18 | + memset(count, 0, sizeof (count)); |
| 19 | + |
| 20 | + unsigned i; |
| 21 | + for(i=0; i<N; ++i) |
| 22 | + count[((source[i])>>(byte*8))&0xff]++; |
| 23 | + |
| 24 | + index[0]=0; |
| 25 | + for(i=1; i<256; ++i) |
| 26 | + index[i] = index[i-1] + count[i-1]; |
| 27 | + |
| 28 | + for(i=0; i<N; ++i) |
| 29 | + dest[index[((source[i])>>(byte*8))&0xff]++] = source[i]; |
| 30 | + } |
| 31 | + |
| 32 | + /** |
| 33 | + * radix sort a given unsigned 32-bit integer array of size N |
| 34 | + */ |
| 35 | + static void radix_sort(uint32_t *source, const unsigned N) { |
| 36 | + uint32_t * temp = new uint32_t[N]; |
| 37 | + radix_(0, N, source, temp); |
| 38 | + radix_(1, N, temp, source); |
| 39 | + radix_(2, N, source, temp); |
| 40 | + radix_(3, N, temp, source); |
| 41 | + |
| 42 | + delete [] temp; |
| 43 | + } |
| 44 | + |
| 45 | + /** |
| 46 | + * check whether the array is in order |
| 47 | + */ |
| 48 | + static void check_order(const uint32_t *data, unsigned N) { |
| 49 | + for(--N ; N > 0; --N, ++data) |
| 50 | + assert(data[0] <= data[1]); |
| 51 | + } |
| 52 | +} |
| 53 | + |
| 54 | +#endif // |
| 55 | + |
| 56 | + |
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