44 lines
1.2 KiB
C++
44 lines
1.2 KiB
C++
// Using standard STL to test the red-black tree in C++
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// In glibc++ this uses <https://github.com/gcc-mirror/gcc/tree/master/libstdc++-v3/src/c++98/tree.cc>
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// With the LLVM libc++ this uses <https://github.com/llvm/llvm-project/blob/main/libcxx/include/__tree>
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// In glibc this uses eventually: <https://sourceware.org/git/?p=glibc.git;a=blob;f=misc/tsearch.c>
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// (Highly optimized in-place red-black tree using the low pointer bit to encode color information.)
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#include <iostream>
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#include <map>
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#include <algorithm>
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using std::for_each;
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typedef int nat;
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struct nat_lt_fn {
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bool operator()(nat const & n1, nat const & n2) const { return n1 < n2; }
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};
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typedef std::map<nat, bool, nat_lt_fn> map;
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map mk_map(unsigned n) {
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map m;
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while (n > 0) {
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--n;
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m.insert(std::make_pair(nat(n), n%10 == 0));
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}
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return m;
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}
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nat fold(map const & m) {
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nat r(0);
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for_each(m.begin(), m.end(), [&](std::pair<nat, bool> const & p) { if (p.second) r = r + nat(1); });
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return r;
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}
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int main(int argc, char ** argv) {
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unsigned n = 4200000;
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if (argc == 2) {
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n = atoi(argv[1]);
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}
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map m = mk_map(n);
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std::cout << fold(m) << "\n";
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return 0;
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}
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