股票推荐系统，并查集

股票推荐系统，并查集

package org.example;

import java.util.*;
public class Main {
    private static int query(List<Integer> parent,int index){//查询根节点
        if(parent.get(index)!=index){
            int tmp=query(parent,parent.get(index));
            parent.set(index,tmp);
        }
        return parent.get(index);
    }
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int q=in.nextInt();
        int gcount=0;
        Map<String,int[]> pMap=new HashMap<>();//记录每个用户的关注的股票数以及其中一支股票的id
        Map<String,Integer> stockIdMap=new HashMap<>();//记录每个股票的id
        ArrayList<Integer> count=new ArrayList<>();//记录每个集合的元素数
        ArrayList<Integer> parent=new ArrayList<>();//记录每个股票的父节点
        for(int k=0;k<q;k++){
            int ops=in.nextInt();
            if(ops==1){//注册
                String name=in.next();
                if(!pMap.containsKey(name)){
                    pMap.put(name,new int[2]);
                }
                int[] cur=pMap.get(name);
                int n=in.nextInt();
                cur[0]=n;
                int root=0;
                for(int i=0;i<n;i++){
                    String stock=in.next();
                    if(!stockIdMap.containsKey(stock)){
                        stockIdMap.put(stock,gcount++);
                        parent.add(gcount-1);
                        count.add(1);
                    }
                    int stockId=stockIdMap.get(stock);
                    if(i==0){
                        cur[1]=stockId;
                        root=query(parent,stockId);
                    }else{
                        int aRoot=query(parent,stockId);
                        if(aRoot!=root){
                            parent.set(aRoot,root);
                            count.set(root,count.get(root)+count.get(aRoot));
                        }
                    }

                }

            }else{//查询
                String name=in.next();
                if(!pMap.containsKey(name)){
                    System.out.println("error");
                    continue;
                }
                int[] cur=pMap.get(name);
                int root=query(parent,cur[1]);
                System.out.println(count.get(root)-cur[0]);
            }
        }
    }

}

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