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Commit 62a9211

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Merge pull request #161 from D3v3sh5ingh/D3v3sh5ingh-patch-3
Radix sorting
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‎Competitive Coding/Sorting/README.md

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* Best case performance O(n log n)
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* Average case performance depends on gap sequence
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####Radix Sorting
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From [Wikipedia](https://en.wikipedia.org/wiki/Radix_sort): radix sort is a non-comparative integer sorting algorithm that sorts data with integer keys by grouping keys by the individual digits which share the same significant position and value. A positional notation is required, but because integers can represent strings of characters (e.g., names or dates) and specially formatted floating point numbers, radix sort is not limited to integers. Radix sort dates back as far as 1887 to the work of Herman Hollerith on tabulating machines.
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__Properties__
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* Worst case performance O(wn)
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* Best case performance O(w + N)
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* Average case performance depends on gap sequence
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###### View the algorithm in [action](https://www.toptal.com/developers/sorting-algorithms/shell-sort)
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### Time-Compexity Graphs
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#ifndef ALGO_RADIX_SORT_H__
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#define ALGO_RADIX_SORT_H__
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#include <stdint.h>
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#include <string.h>
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#include <stdlib.h>
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#include <assert.h>
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#include <generic.h>
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#include <memory>
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namespace alg {
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/**
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* couting sort
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*/
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static void radix_(int byte, const unsigned N, const uint32_t *source, uint32_t *dest) {
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unsigned count[256];
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unsigned index[256];
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memset(count, 0, sizeof (count));
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unsigned i;
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for(i=0; i<N; ++i)
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count[((source[i])>>(byte*8))&0xff]++;
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index[0]=0;
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for(i=1; i<256; ++i)
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index[i] = index[i-1] + count[i-1];
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for(i=0; i<N; ++i)
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dest[index[((source[i])>>(byte*8))&0xff]++] = source[i];
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}
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/**
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* radix sort a given unsigned 32-bit integer array of size N
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*/
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static void radix_sort(uint32_t *source, const unsigned N) {
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uint32_t * temp = new uint32_t[N];
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radix_(0, N, source, temp);
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radix_(1, N, temp, source);
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radix_(2, N, source, temp);
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radix_(3, N, temp, source);
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delete [] temp;
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}
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/**
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* check whether the array is in order
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*/
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static void check_order(const uint32_t *data, unsigned N) {
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for(--N ; N > 0; --N, ++data)
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assert(data[0] <= data[1]);
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}
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}
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#endif //
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