52 lines
1.4 KiB
Rust
52 lines
1.4 KiB
Rust
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import option::none;
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import option::some;
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// A very naive implementation of union-find with unsigned integer nodes.
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// Maintains the invariant that the root of a node is always equal to or less
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// than the node itself.
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type node = option::t[uint];
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type ufind = {nodes: @mutable [mutable node]};
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fn make() -> ufind { ret {nodes: @mutable ~[mutable]}; }
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fn make_set(ufnd: &ufind) -> uint {
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let idx = ivec::len(*ufnd.nodes);
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*ufnd.nodes += ~[mutable none[uint]];
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ret idx;
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}
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/// Creates sets as necessary to ensure that least `n` sets are present in the
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/// data structure.
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fn grow(ufnd: &ufind, n: uint) {
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while set_count(ufnd) < n { make_set(ufnd); }
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}
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fn find(ufnd: &ufind, n: uint) -> uint {
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alt ufnd.nodes.(n) {
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none. { ret n; }
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some(m) { let m_ = m; be find(ufnd, m_); }
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}
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}
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fn union(ufnd: &ufind, m: uint, n: uint) {
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let m_root = find(ufnd, m);
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let n_root = find(ufnd, n);
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if m_root < n_root {
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ufnd.nodes.(n_root) = some[uint](m_root);
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} else if (m_root > n_root) { ufnd.nodes.(m_root) = some[uint](n_root); }
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}
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fn set_count(ufnd: &ufind) -> uint { ret ivec::len[node](*ufnd.nodes); }
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// Removes all sets with IDs greater than or equal to the given value.
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fn prune(ufnd: &ufind, n: uint) {
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// TODO: Use "slice" once we get rid of "mutable?"
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let len = ivec::len[node](*ufnd.nodes);
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while len != n { ivec::pop[node](*ufnd.nodes); len -= 1u; }
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}
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