MergeUnionFind
(C++/ds/uf/MergeUF.hpp)

• View this file on GitHub
• Last update: 2025-06-11 17:30:11+09:00
• Include: #include "C++/ds/uf/MergeUF.hpp"

Depends on

• UnionFind (C++/ds/uf/UnionFind.hpp)

Code

#pragma once

#include "C++/ds/uf/UnionFind.hpp"
namespace man {
template <class T> struct MergeUF: UnionFind {
    using UnionFind::par;
    using UnionFind::operator[];
    using UnionFind::size;
    using UnionFind::groups;
    MergeUF(const int n): UnionFind(n){}
    ~MergeUF(){}
    virtual T get(const int i) = 0;
    virtual void merge(const int i, const int j) = 0;
    bool unite(int x, int y) {
        x = (*this)[x], y = (*this)[y];
        if(x == y) {
            return false;
        }
        if(-par[x] < -par[y]) {
            std::swap(x, y);
        }
        par[x] += par[y], par[y] = x;
		merge(x, y);
		return true;
	}
};
}
/**
 * @brief MergeUnionFind
 */

#line 2 "C++/ds/uf/MergeUF.hpp"

#line 2 "C++/ds/uf/UnionFind.hpp"

#include <cassert>

#include <vector>

#include <algorithm>

namespace man {
struct UnionFind {
protected:
    std::vector<int> par;
public:
    UnionFind(const int n): par(n, -1){}
    inline int operator[](int i) noexcept {
        while(par[i] >= 0) {
            const int p = par[par[i]];
            if(p < 0) return par[i];
            i = par[i] = p;
        }
        return i;
    }
    inline bool unite(int x, int y) noexcept {
        x = (*this)[x], y = (*this)[y];
        if(x == y) return false;
        if(-par[x] < -par[y]) {
            std::swap(x, y);
        }
        par[x] += par[y], par[y] = x;
        return true;
    }
    inline int size(const int x) noexcept {
        return -par[(*this)[x]];
    }
    inline int size() const noexcept { return par.size(); }
    inline std::vector<std::vector<int>> groups() noexcept {
        const int n = std::ssize(par);
        std::vector<std::vector<int>> res(n);
        for(int i = 0; i < n; ++i) {
            res[(*this)[i]].emplace_back(i);
        }
        const auto it = std::ranges::remove_if(res, [&](const std::vector<int> &v){ return v.empty(); });
        res.erase(it.begin(), it.end());
        return res;
    }
};

inline bool is_bipartite(UnionFind uf) noexcept {
    assert(uf.size() % 2 == 0);
    const int n = uf.size() / 2;
    bool ok = true;
    for(int i = 0; i < n; ++i) {
        ok &= uf[i] != uf[i + n];
    }
    return ok;
}
}
/**
 * @brief UnionFind
 * @see https://github.com/maspypy/library/blob/main/ds/unionfind/unionfind.hpp
 */
#line 4 "C++/ds/uf/MergeUF.hpp"
namespace man {
template <class T> struct MergeUF: UnionFind {
    using UnionFind::par;
    using UnionFind::operator[];
    using UnionFind::size;
    using UnionFind::groups;
    MergeUF(const int n): UnionFind(n){}
    ~MergeUF(){}
    virtual T get(const int i) = 0;
    virtual void merge(const int i, const int j) = 0;
    bool unite(int x, int y) {
        x = (*this)[x], y = (*this)[y];
        if(x == y) {
            return false;
        }
        if(-par[x] < -par[y]) {
            std::swap(x, y);
        }
        par[x] += par[y], par[y] = x;
		merge(x, y);
		return true;
	}
};
}
/**
 * @brief MergeUnionFind
 */

Back to top page