// Most significant digit radix sort (recursive)
void msd_radix_sort(int *first, int *last, int msb = 31)
{
if (first != last && msb >= 0)
{
int *mid = std::partition(first, last, radix_test(msb));
msb--; // decrement most-significant-bit
msd_radix_sort(first, mid, msb); // sort left partition
msd_radix_sort(mid, last, msb); // sort right partition
}
}
int main(void)
{
out("starting ...\n");
std::cout << " MSD radix sort " << std::endl;
std::vector<std::string> strings;
int N = 0;
//start from
char str[256] = {0};
while( scanf("%s",&str) != EOF ) {
strings.push_back(str);
}
N = strings.size();
std::vector<int> v(N); //map to sorted strings
for(int i = 0; i < N; i++)
v[i] = i; //all v's entries point to initial respective locations
std::vector<int> aux(N); //map to sorted strings
msd_radix_sort(strings, v, aux, 0, N, 0);
out("SORTED strings\n");
for(int i = 0; i < N; i++) {
std::cout << strings[v[i]] << std::endl;
}
return 0;
}
//recursive call, first we count sort on the leftmost column,
//then we proceed to recursively sort the next column
//aux is passed so we dont reallocate every time the helper array
void msd_radix_sort(const std::vector<std::string> & strings, std::vector<int> &v, std::vector<int> &aux, int start, int end, int chrindx)
{
out("msd_radix_sort %d, %d, %d\n", start, end, chrindx);
if(end - start < 2) return;
if(end - start < 24) {
insertion_sort(strings, v, aux, start, end, chrindx);
return;
}
for(int i = start; i < end; i++) {
out("h %s\n", strings[v[i]].c_str());
}
int counts[R + 1] = {0};
counting_sort(strings, v, aux, start, end, chrindx, counts);
for(int r = 0; r < R; r++) {
if(counts[r+1] - counts[r] > 1) {
msd_radix_sort(strings, v, aux, start + counts[r],
start + counts[r + 1], chrindx + 1);
}
}
for(int i = start; i < end; i++) {
out("s %s\n", strings[v[i]].c_str());
}
}
