44 lines
957 B
C++
44 lines
957 B
C++
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class quick_union {
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public:
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size_t n;
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vector<size_t> c, sz;
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vector<pair<size_t, size_t>> history;
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public:
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quick_union(size_t n) : n(n), c(n), sz(n) {
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iota(c.begin(), c.end(), 0);
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sz.assign(n, 1);
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}
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size_t query(size_t i) {
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if (c[i] != i) return query(c[i]);
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return c[i];
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}
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void merge(size_t i, size_t j) {
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if (connected(i, j)) {
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history.emplace_back(n, n);
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} else {
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i = query(i), j = query(j);
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if (sz[i] > sz[j]) swap(i, j);
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history.emplace_back(i, j);
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sz[j] += sz[i];
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c[i] = j;
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}
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}
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bool connected(size_t i, size_t j) {
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return query(i) == query(j);
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}
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size_t query_size(size_t i) {
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return sz[query(i)];
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}
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void rollback() {
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auto [i, j] = popback(history);
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if (i == n and j == n) return;
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c[i] = i;
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sz[j] -= sz[i];
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}
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};
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