HDU 3974 Assign the task （并查集&线段树）

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题目链接

虽然挂在线段树的题集里，但是能一眼看出也是并查集的题。本来准备就用线段树做，可是，想了半天不知道怎么建树。。。就先用并查集过吧。等忙完期末项目，回来再看看怎么用线段树做。

并查集代码：

import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.util.Arrays;import java.util.Scanner;public class Main {static Scanner sc = new Scanner(System.in);static BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));static int T,n,m,newTime,newTask;static int [] dad;static int [] mis;static int [] tim;static void find(int x){while(dad[x] != x){if(newTime < tim[x]){//newTime小则应跟随大的时间更新newTime = tim[x];newTask = mis[x];}x = dad[x];}if(newTime < tim[x]){//与最终boss比较newTime = tim[x];newTask = mis[x];}}public static void main(String[] args) throws IOException {T = sc.nextInt();for(int t = 1; t <= T; t++){System.out.println("Case #"+t+":");n = sc.nextInt();dad = new int[n+1];for(int i = 1; i <= n; i++)dad[i] = i;mis = new int[n+1];Arrays.fill(mis, -1);tim = new int[n+1];Arrays.fill(tim, 0);int u,v;for(int i = 0; i < n - 1; i++){u = sc.nextInt(); v = sc.nextInt();dad[u] = v;}m = sc.nextInt();String op;int emp,task,k = 0;for(int i = 0; i < m; i++){op = sc.next();if(op.equals("C")){emp = sc.nextInt();newTime = 0;newTask = mis[emp];find(emp);System.out.println(newTask);}else{emp = sc.nextInt(); task = sc.nextInt();mis[emp] = task;tim[emp] = ++k;}}}}}

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