非递归并查集——zoj4109

卡常卡的我难受

非递归并查集好像写起来常数小一点

int F[maxn];
int Find(int x){
    int r = x;
    while (F[r] != r)r = F[r];
    int i = x,j;
    while (F[i] != r){
        j = F[i];
        F[i] = r;
        i = j;
    }
    return r;
}
void Union(int u,int v){
    int f1=Find(u),f2=Find(v);
    if(f1!=f2){
        if(f1>f2)swap(f1,f2);
        F[f2]=f1;
    }
}

下面是完整代码

#include<bits/stdc++.h>
using namespace std;
#define maxn 1000005
vector<int> G[maxn];
int n,m;

int F[maxn];
int Find(int x){
    int r = x;
    while (F[r] != r)r = F[r];
    int i = x,j;
    while (F[i] != r){
        j = F[i];
        F[i] = r;
        i = j;
    }
    return r;
}
void Union(int u,int v){
    int f1=Find(u),f2=Find(v);
    if(f1!=f2){
        if(f1>f2)swap(f1,f2);
        F[f2]=f1;
    }
}

int vis[maxn],ans[maxn],tt;
priority_queue<int,vector<int>, greater<int> >pq;

void init(){
    tt=;
    for(int i=;i<=n;i++)G[i].clear(),F[i]=i,vis[i]=;
    while(pq.size())pq.pop();
}
void addedge(int u,int v){G[u].push_back(v);}
int main(){
    int t;
    cin>>t;while(t--){
        scanf("%d%d",&n,&m);
            init();
        for(int i=;i<=m;i++){
            int u,v;
            scanf("%d%d",&u,&v);
            addedge(u,v);addedge(v,u);
            Union(u,v);
        }

        for(int i=;i<=n;i++)
            if(Find(i)==i)pq.push(i);
        cout<<pq.size()<<endl;

        while(!pq.empty()){
            int cur=pq.top();pq.pop();
            if(vis[cur])continue;
            vis[cur]=;
            ans[++tt]=cur;
            for(int i=;i<G[cur].size();i++){
                int v=G[cur][i];
                if(vis[v])continue;
                pq.push(v);
            }
        }
        for(int i=;i<tt;i++)cout<<ans[i]<<" ";
        cout<<ans[tt]<<endl;
    }
}