dsu.hpp

[詳解]

#pragma once
#include"../../kyopro_library/template.hpp"
 
/// @brief Disjoint Set Union
struct DSU {
    DSU()=default;
 
    DSU(int n) {
        par=vector<int>(n); iota(par.begin(),par.end(),0);
        sz=vector<int>(n,1);
        forest_count=n;
    }
 
    int find(int x) {
        if(par[x]==x) return x;
        return par[x]=find(par[x]);
    }
 
    bool merge(int x, int y) {
        x=find(x); y=find(y);
        if(x==y) return false;
        if(sz[x]<sz[y]) swap(x,y);
        par[y]=x; sz[x]+=sz[y];
        forest_count--;
        return true;
    }
 
    int size(int x) { return sz[find(x)]; }
 
    bool same(int x, int y) { return find(x)==find(y); }
 
    int count() { return forest_count; }
 
    vector<vector<int>> groups() {
        int n=par.size();
        vector<vector<int>> ret(n);
        for(int i=0; i<n; i++) ret[find(i)].push_back(i);
        ret.erase(remove_if(ret.begin(),ret.end(),[&](const vector<int>& v) { return v.empty(); }),ret.end());
        return ret;
    }
 
private:
    vector<int> par,sz;
    int forest_count;
};