题解 | #特征提取#

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);

        while(in.hasNext()){
            solution1(in);
            // solution2(in);
        }
    }

    /**
     * 模拟法: Map
     * @param in
     */
    private static void solution1(Scanner in){
        int cases = in.nextInt();

        while(cases-- > 0){
            int frames = in.nextInt();

            HashMap<String, Integer> lastMap = new HashMap<>();
            HashMap<String, Integer> currMap;

            int num = in.nextInt();
            while(num-- > 0){
                lastMap.put(new Identity(in.nextInt(), in.nextInt()).toString(), 1);
            }

            int tmp;
            int max = 1;
            for(int i=2; i<=frames; i++){
                currMap = new HashMap<>();
                num = in.nextInt();
                Identity identity;
                while(num-- > 0){
                    identity = new Identity(in.nextInt(), in.nextInt());
                    if(lastMap.containsKey(identity.toString())){
                        tmp = lastMap.get(identity.toString()) + 1;
                        max = Math.max(max, tmp);
                        currMap.put(identity.toString(), tmp);
                    }else{
                        currMap.put(identity.toString(), 1);
                    }
                }
                lastMap = currMap;
            }

            System.out.println(max);
        }
    }


    /**
     * 模拟法: List
     * @param in
     */
    private static void solution2(Scanner in){
        int cases = in.nextInt();

        while(cases-- > 0){
            List<Identity> identityList = new ArrayList<>();
            int frames = in.nextInt();
            for(int i=1; i<=frames; i++){
                int num = in.nextInt();
                while(num-- > 0){
                    identityList.add(new Identity(i, in.nextInt(), in.nextInt()));
                }
            }

            identityList.sort((o1, o2) -> {
                if(o1.x != o2.x){
                    return o1.x - o2.x;
                }else{
                    return o1.y - o2.y;
                }
            });

            int size = identityList.size();
            int tmp = 1;
            int max = 1;
            for(int i=1; i<size; i++){
                if(identityList.get(i).equals(identityList.get(i-1))){
                    tmp++;
                    max = Math.max(max, tmp);
                }else{
                    tmp = 1;
                }
            }

            System.out.println(max);
        }
    }

    private static class Identity{
        int frameId;
        int x;
        int y;

        public Identity(int frameId, int x, int y){
            this.frameId = frameId;
            this.x = x;
            this.y = y;
        }

        public Identity(int x, int y){
            this.x = x;
            this.y = y;
        }

        @Override
        public String toString(){
            return x+","+y;
        }

        @Override
        public boolean equals(Object o){
            if(this == o){
                return true;
            }
            if(o == null || getClass() != o.getClass()){
                return false;
            }
            Identity identity = (Identity) o;
            return frameId == identity.frameId+1 && x == identity.x && y == identity.y;
        }
    }
}