poj 2524 并查集

第二次初探并查集，poj2524，一次AC，挺高兴的，呵呵！

ps：这道题是求在一个大学里面有的学生信仰多少个不同的宗教，注意一点就是下面没出现的学生，视为他们各自信仰不同的宗教。

import java.util.Scanner; public class Main{ static int[] r; //static int[] rank; public static void main(String[] args) { Scanner sc = new Scanner(System.in); int casenumber = 0; while (sc.hasNext()) { int n = sc.nextInt(); int m = sc.nextInt(); if (n == 0 && m == 0) break; casenumber++; r = new int[n + 1]; //rank = new int[n + 1]; //Arrays.fill(rank, 1); for (int i = 1; i <= n; ++i) { r[i] = i; } for (int i = 0; i < m; ++i) { int x = sc.nextInt(); int y = sc.nextInt(); merge(x, y); } int ans = 0; // TreeSet<Integer> re = new TreeSet<Integer>(); int[] re = new int[n + 1]; for (int i = 1; i <= n; ++i) { if (r[i] == i) { if (re[i] == 0) { ++ans; re[i] = 1; } } else { if (re[find(i)] == 0) { ++ans; re[i] = 1; } } } System.out.println("Case " + casenumber + ": " + ans); } } static void merge(int x, int y) { int px = find(x); int py = find(y); if (px == py) return; // System.out.println(rank[px]+";"+rank[py]); if (px <= py) { r[py] = px; // rank[px] = rank[py] + rank[px]; } else { r[px] = py; // rank[py] = rank[py] + rank[px]; // /System.out.println(rank[py]); } } static int find(int x) { if (r[x] == x) return x; return find(r[x]); } }