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added merge sort

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This commit is contained in:
Ahmet Inan 2024-03-08 09:53:28 +01:00
commit d319189d7a
2 changed files with 37 additions and 7 deletions
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25
sort.hh
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@ -34,5 +34,30 @@ static void insertion_sort(INDEX *p, TYPE *a, int n)
}
}
template <typename TYPE, int MAX_N>
class MergeSort
{
TYPE tmp[MAX_N];
void merge(TYPE *a, int n, int left, int right, int end)
{
if (right > n)
right = n;
if (end > n)
end = n;
for (int i = left, j = right, k = left; k < end; ++k)
tmp[k] = (i < right && (j >= end || a[i] <= a[j])) ? a[i++] : a[j++];
}
public:
void operator()(TYPE *a, int n)
{
for (int l = 1; l < n; l *= 2) {
for (int i = 0; i < n; i += 2*l)
merge(a, n, i, i+l, i+2*l);
for (int i = 0; i < n; ++i)
a[i] = tmp[i];
}
}
};
}

19
tests/sort_regression_test.cc
View file

@ -13,25 +13,30 @@ Copyright 2024 Ahmet Inan <inan@aicodix.de>
int main()
{
const int MAX_N = 128;
std::random_device rd;
typedef std::default_random_engine generator;
typedef std::uniform_int_distribution<int> distribution;
auto rand = std::bind(distribution(1, 32), generator(rd()));
int a[32], b[32], c[32], d[32], e[32], f[32];
auto rand = std::bind(distribution(1, MAX_N), generator(rd()));
int a[MAX_N], b[MAX_N], c[MAX_N], d[MAX_N], e[MAX_N], f[MAX_N], g[MAX_N];
CODE::MergeSort<int, MAX_N> merge_sort;
for (int loop = 0; loop < 1000000; ++loop) {
int size = rand();
for (int i = 0; i < size; ++i)
a[i] = b[i] = c[i] = d[i] = rand();
a[i] = b[i] = c[i] = d[i] = e[i] = rand();
std::sort(a, a+size);
CODE::insertion_sort(b, size);
for (int i = 0; i < size; ++i)
assert(a[i] == b[i]);
merge_sort(c, size);
for (int i = 0; i < size; ++i)
e[i] = i;
std::stable_sort(e, e+size, [c](int i, int j){ return c[i] < c[j]; });
CODE::insertion_sort(f, d, size);
assert(a[i] == c[i]);
for (int i = 0; i < size; ++i)
assert(e[i] == f[i]);
f[i] = i;
std::stable_sort(f, f+size, [d](int i, int j){ return d[i] < d[j]; });
CODE::insertion_sort(g, e, size);
for (int i = 0; i < size; ++i)
assert(f[i] == g[i]);
}
std::cerr << "Sorting regression test passed!" << std::endl;
return 0;