52 lines
1.4 KiB
Rust
52 lines
1.4 KiB
Rust
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import option::{some, none};
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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 = {mutable nodes: [mutable node]};
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fn make() -> ufind { ret {mutable nodes: [mutable]}; }
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fn make_set(ufnd: ufind) -> uint {
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let idx = vec::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 vec::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 = vec::len::<node>(ufnd.nodes);
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while len != n { vec::pop::<node>(ufnd.nodes); len -= 1u; }
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}
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