POJ1988 带权并查集

来源：互联网发布：js 转化成数字类型编辑：程序博客网时间：2024/06/04 18:02

题意:

若干个个方块，2种操作：

M 将u所在的方块堆整体移动到v所在的方块堆；

C 询问u方块下面有多少块方块。

做法：带权并查集

1）对于每个根节点，拥有属性SetSize【root】，即此集合的大小；

2）对于每个节点，拥有属性distanceToRoot【u】，即此节点距离所在集合根节点的距离，根节点离自己距离为0

3）在压缩路径，递归操作时，维护的是distanceToRoot 值；

4）在合并操作时，维护的是SetSize【fromRoot】与 distanceToRoot【toRoot】

import java.io.BufferedReader;import java.io.InputStream;import java.io.InputStreamReader;import java.io.PrintWriter;import java.math.BigInteger;import java.util.StringTokenizer;public class Main {public static void main(String[] args) {new POJ1988().solve();}}class POJ1988 {InputReader in = new InputReader(System.in);PrintWriter out = new PrintWriter(System.out);final int N = 30008 ;int[] father = new int[N] ;int[] distanceToRoot = new int[N] ;int[] setSize = new int[N] ;void init(){for(int i = 1 ; i < N ; i++){father[i] = i ;setSize[i] = 1 ;distanceToRoot[i] = 0 ; }}int getRoot(int u){if(u == father[u]) return u ;int root = getRoot(father[u])  ;distanceToRoot[u] += distanceToRoot[father[u]] ;return father[u] = root ;}void move(int from , int to){int rootFrom = getRoot(from) ;int rootTo = getRoot(to) ;if(rootFrom != rootTo){father[rootTo] = rootFrom ;distanceToRoot[rootTo] += setSize[rootFrom] ;setSize[rootFrom] += setSize[rootTo] ;}}void solve() {init() ;int n = in.nextInt() ; while(n-- > 0){if("C".equals(in.next())){int u = in.nextInt() ;int root = getRoot(u) ;    out.println(setSize[root] - distanceToRoot[u] - 1) ;}else{move(in.nextInt() , in.nextInt()) ;}}out.flush() ;}}class InputReader {public BufferedReader reader;public StringTokenizer tokenizer;public InputReader(InputStream stream) {reader = new BufferedReader(new InputStreamReader(stream), 32768);tokenizer = new StringTokenizer("");}private void eat(String s) {tokenizer = new StringTokenizer(s);}public String nextLine() {try {return reader.readLine();} catch (Exception e) {return null;}}public boolean hasNext() {while (!tokenizer.hasMoreTokens()) {String s = nextLine();if (s == null)return false;eat(s);}return true;}public String next() {hasNext();return tokenizer.nextToken();}public int nextInt() {return Integer.parseInt(next());}public long nextLong() {return Long.parseLong(next());}public double nextDouble() {return Double.parseDouble(next());}public BigInteger nextBigInteger() {return new BigInteger(next());}}

0 0