[藍橋杯] 國王的煩惱 並查集+思維

題面：

思路：

由於存在刪邊操作，正着來處理可能不太好寫，但正難則反，我們可以反向來思考這個問題，我們可以按天數從大到小排序，那麼刪邊操作

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.StreamTokenizer;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) throws IOException {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader sc = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Task solver = new Task();
        solver.solve(1, sc, out);
        out.close();
    }

    static class Task {
    	public int[] pre;
    	
    	public int find(int x) {
    		int temp=x;
    		while(temp!=pre[temp])
    				temp=pre[temp];
    		int i=x,j;
    		while(i!=temp) {
    			j=pre[i];
    			pre[i]=temp;
    			i=j;
    		}
    		return temp;
    	}
    	
    	public boolean join(int x,int y) {
    		int a=find(x);
    		int b=find(y);
    		if(a!=b) {
    			pre[a]=b;
    			return false;
    		}
    		return true;
    	}
    	
        public void solve(int testNumber, InputReader sc, PrintWriter out) throws IOException {
        	int n=sc.nextInt();
        	int m=sc.nextInt();
        	pre=new int[n+1];
        	for(int i=1;i<=n;i++)
        		pre[i]=i;
        	TreeMap<Integer,ArrayList<int[]>> G=new TreeMap<>(new Comparator<Integer>() {
				@Override
				public int compare(Integer o1, Integer o2) {
					return o2-o1;
				}
        	});
        	for(int i=0;i<m;i++) {
        		int a=sc.nextInt();
        		int b=sc.nextInt();
        		int t=sc.nextInt();
        		int[] path=new int[2];
        		path[0]=a;
        		path[1]=b;
        		ArrayList<int[]> temp=G.get(t);
        		if(temp==null)
        			temp=new ArrayList<int[]>();
        		temp.add(path);
        		G.put(t, temp);
        	}
        	int ans=0;
        	for(Map.Entry<Integer, ArrayList<int[]>> temp:G.entrySet()) {
        		boolean flag=false;
        		for(int[] p:temp.getValue()) {
        			if(!join(p[0],p[1])){
        				if(!flag)
        					ans++;
        				flag=true;
        			}
        		}
        	}
        	out.println(ans);
        }
    }
   
    static class InputReader{
        StreamTokenizer tokenizer;
        public InputReader(InputStream stream){
            tokenizer=new StreamTokenizer(new BufferedReader(new InputStreamReader(stream)));
            tokenizer.ordinaryChars(33,126);
            tokenizer.wordChars(33,126);
        }
        public String next() throws IOException {
            tokenizer.nextToken();
            return tokenizer.sval;
        }
        public int nextInt() throws IOException {
            return Integer.parseInt(next());
        }
        public long nextLong() throws IOException {
            return Long.parseLong(next());
        }
        public boolean hasNext() throws IOException {
            int res=tokenizer.nextToken();
            tokenizer.pushBack();
            return res!=tokenizer.TT_EOF;
        }
        
        public double nextDouble() throws NumberFormatException, IOException {
        	return Double.parseDouble(next());
        }
        
        public BigInteger nextBigInteger() throws IOException {
        	return new BigInteger(next());
        }
    }
}

就轉化爲加邊就十分容易處理了。