test/unit/rollback_dsu.test.cpp

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• Last update: 2026-10-26 01:30:50+09:00
• Problem: http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ITP1_1_A

Depends on

• Rollback DSU (datastructure/rollback_dsu.hpp)

Code

#define PROBLEM "http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ITP1_1_A"
#include <cassert>
#include <iostream>
#include <random>
#include <vector>

#include "atcoder/dsu"
#include "datastructure/rollback_dsu.hpp"

int main() {
    std::mt19937 rng(99);
    for (int it = 0; it < 300; it++) {
        int n = 1 + rng() % 10;
        rollback_dsu d(n);
        std::vector<std::pair<int, int>> merged;  // current edge list
        std::vector<std::pair<int, int>> stack_sizes;
        auto check = [&] {
            atcoder::dsu ref(n);
            for (auto [a, b] : merged) ref.merge(a, b);
            for (int a = 0; a < n; a++) {
                for (int b = 0; b < n; b++) assert(d.same(a, b) == ref.same(a, b));
                assert(d.size(a) == ref.size(a));
            }
            assert(d.groups() == ref.groups());
            assert(d.time() == int(merged.size()));
        };
        for (int q = 0; q < 60; q++) {
            int op = rng() % 3;
            if (op == 0 || merged.empty()) {
                int a = rng() % n, b = rng() % n;
                int l = d.merge(a, b);
                merged.emplace_back(a, b);
                assert(l == d.leader(a) && l == d.leader(b));
            } else if (op == 1) {
                d.undo();
                merged.pop_back();
            } else {
                int t = rng() % (merged.size() + 1);
                d.rollback(t);
                merged.resize(t);
            }
            check();
        }
    }
    std::cout << "Hello World" << std::endl;
    return 0;
}

#line 1 "test/unit/rollback_dsu.test.cpp"
#define PROBLEM "http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ITP1_1_A"
#include <cassert>
#include <iostream>
#include <random>
#include <vector>

#line 1 "atcoder/dsu.hpp"



#include <algorithm>
#line 7 "atcoder/dsu.hpp"

namespace atcoder {

// Implement (union by size) + (path compression)
// Reference:
// Zvi Galil and Giuseppe F. Italiano,
// Data structures and algorithms for disjoint set union problems
struct dsu {
  public:
    dsu() : _n(0) {}
    explicit dsu(int n) : _n(n), parent_or_size(n, -1) {}

    int merge(int a, int b) {
        assert(0 <= a && a < _n);
        assert(0 <= b && b < _n);
        int x = leader(a), y = leader(b);
        if (x == y) return x;
        if (-parent_or_size[x] < -parent_or_size[y]) std::swap(x, y);
        parent_or_size[x] += parent_or_size[y];
        parent_or_size[y] = x;
        return x;
    }

    bool same(int a, int b) {
        assert(0 <= a && a < _n);
        assert(0 <= b && b < _n);
        return leader(a) == leader(b);
    }

    int leader(int a) {
        assert(0 <= a && a < _n);
        return _leader(a);
    }

    int size(int a) {
        assert(0 <= a && a < _n);
        return -parent_or_size[leader(a)];
    }

    std::vector<std::vector<int>> groups() {
        std::vector<int> leader_buf(_n), group_size(_n);
        for (int i = 0; i < _n; i++) {
            leader_buf[i] = leader(i);
            group_size[leader_buf[i]]++;
        }
        std::vector<std::vector<int>> result(_n);
        for (int i = 0; i < _n; i++) {
            result[i].reserve(group_size[i]);
        }
        for (int i = 0; i < _n; i++) {
            result[leader_buf[i]].push_back(i);
        }
        result.erase(
            std::remove_if(result.begin(), result.end(),
                           [&](const std::vector<int>& v) { return v.empty(); }),
            result.end());
        return result;
    }

  private:
    int _n;
    // root node: -1 * component size
    // otherwise: parent
    std::vector<int> parent_or_size;

    int _leader(int a) {
        if (parent_or_size[a] < 0) return a;
        return parent_or_size[a] = _leader(parent_or_size[a]);
    }
};

}  // namespace atcoder


#line 4 "datastructure/rollback_dsu.hpp"
#include <utility>
#line 6 "datastructure/rollback_dsu.hpp"
struct rollback_dsu {
public:
    rollback_dsu() : rollback_dsu(0) {
    }
    explicit rollback_dsu(int n) : _n(n), parent_or_size(n, -1) {
    }
    int merge(int a, int b) {
        assert(0 <= a && a < _n);
        assert(0 <= b && b < _n);
        int x = leader(a), y = leader(b);
        if (x == y) {
            history.emplace_back(-1, -1);
            return x;
        }
        if (-parent_or_size[x] < -parent_or_size[y]) std::swap(x, y);
        history.emplace_back(y, parent_or_size[y]);
        parent_or_size[x] += parent_or_size[y];
        parent_or_size[y] = x;
        return x;
    }
    void undo() {
        assert(!history.empty());
        auto [y, s] = history.back();
        history.pop_back();
        if (y == -1) return;
        parent_or_size[parent_or_size[y]] -= s;
        parent_or_size[y] = s;
    }
    int time() const {
        return int(history.size());
    }
    void rollback(int t) {
        assert(0 <= t && t <= time());
        while (time() > t) undo();
    }
    bool same(int a, int b) const {
        assert(0 <= a && a < _n);
        assert(0 <= b && b < _n);
        return leader(a) == leader(b);
    }
    int leader(int a) const {
        assert(0 <= a && a < _n);
        while (parent_or_size[a] >= 0) a = parent_or_size[a];
        return a;
    }
    int size(int a) const {
        assert(0 <= a && a < _n);
        return -parent_or_size[leader(a)];
    }
    std::vector<std::vector<int>> groups() const {
        std::vector<int> leader_buf(_n), group_size(_n);
        for (int i = 0; i < _n; i++) {
            leader_buf[i] = leader(i);
            group_size[leader_buf[i]]++;
        }
        std::vector<std::vector<int>> result(_n);
        for (int i = 0; i < _n; i++) result[i].reserve(group_size[i]);
        for (int i = 0; i < _n; i++) result[leader_buf[i]].push_back(i);
        result.erase(std::remove_if(result.begin(), result.end(),
                                    [&](const std::vector<int>& v) { return v.empty(); }),
                     result.end());
        return result;
    }

private:
    int _n;
    std::vector<int> parent_or_size;
    std::vector<std::pair<int, int>> history;  // (attached leader, its old parent_or_size)
};
#line 9 "test/unit/rollback_dsu.test.cpp"

int main() {
    std::mt19937 rng(99);
    for (int it = 0; it < 300; it++) {
        int n = 1 + rng() % 10;
        rollback_dsu d(n);
        std::vector<std::pair<int, int>> merged;  // current edge list
        std::vector<std::pair<int, int>> stack_sizes;
        auto check = [&] {
            atcoder::dsu ref(n);
            for (auto [a, b] : merged) ref.merge(a, b);
            for (int a = 0; a < n; a++) {
                for (int b = 0; b < n; b++) assert(d.same(a, b) == ref.same(a, b));
                assert(d.size(a) == ref.size(a));
            }
            assert(d.groups() == ref.groups());
            assert(d.time() == int(merged.size()));
        };
        for (int q = 0; q < 60; q++) {
            int op = rng() % 3;
            if (op == 0 || merged.empty()) {
                int a = rng() % n, b = rng() % n;
                int l = d.merge(a, b);
                merged.emplace_back(a, b);
                assert(l == d.leader(a) && l == d.leader(b));
            } else if (op == 1) {
                d.undo();
                merged.pop_back();
            } else {
                int t = rng() % (merged.size() + 1);
                d.rollback(t);
                merged.resize(t);
            }
            check();
        }
    }
    std::cout << "Hello World" << std::endl;
    return 0;
}

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