結果

問題 No.1254 補強への架け橋
ユーザー uwi
提出日時 2020-10-09 21:51:33
言語 Java
(openjdk 23)
結果
AC  
実行時間 370 ms / 2,000 ms
コード長 5,425 bytes
コンパイル時間 5,397 ms
コンパイル使用メモリ 81,140 KB
実行使用メモリ 51,340 KB
最終ジャッジ日時 2024-07-20 10:45:41
合計ジャッジ時間 25,806 ms
ジャッジサーバーID
（参考情報） 		judge2 / judge3
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 3
other AC * 123
権限があれば一括ダウンロードができます

ソースコード

diff # 

package contest201009;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.List;

public class F {
	InputStream is;
	PrintWriter out;
	String INPUT = "";
	
	void solve()
	{
		int n = ni();
		int m = n;
		int[] from = new int[m];
		int[] to = new int[m];
		for(int i = 0;i < m;i++){
		    from[i] = ni()-1;
		    to[i] = ni()-1;
		}
		int[][] g = packU(n, from, to);
		int[] clus = decomposeToBECCNoRec(g);
		List<Integer> ret = new ArrayList<>();
		for(int i = 0;i < m;i++){
			if(clus[from[i]] == clus[to[i]])ret.add(i+1);
		}
		out.println(ret.size());
		for(int v : ret){
			out.print(v + " ");
		}
		out.println();
	}

	public static int[][] packU(int n, int[] from, int[] to) {
		return packU(n, from, to, from.length);
	}

	public static int[][] packU(int n, int[] from, int[] to, int sup) {
		int[][] g = new int[n][];
		int[] p = new int[n];
		for (int i = 0; i < sup; i++) p[from[i]]++;
		for (int i = 0; i < sup; i++) p[to[i]]++;
		for (int i = 0; i < n; i++) g[i] = new int[p[i]];
		for (int i = 0; i < sup; i++) {
			g[from[i]][--p[from[i]]] = to[i];
			g[to[i]][--p[to[i]]] = from[i];
		}
		return g;
	}


	public static int[] decomposeToBECCNoRec(int[][] g)
	{
		int n = g.length;
		boolean[] visited = new boolean[n];
		int[] ord = new int[n];
		int[] low = new int[n];

		int[] ids = new int[n];
		int[] inds = new int[n];
		int[] parct = new int[n];
		int pos = 0;
		for(int i = 0;i < n;i++){
			if(!visited[i]){
				ids[0] = i;
				inds[0] = 0;
				int sp = 1;
				while(sp > 0){
					int cur = ids[sp-1];
					if(inds[sp-1] == 0){
						visited[cur] = true;
						ord[cur] = low[cur] = pos++;
						parct[sp-1] = 0;
					}
					if(inds[sp-1] == g[cur].length){
						if(sp-2 >= 0)low[ids[sp-2]] = Math.min(low[ids[sp-2]], low[cur]);
						sp--;
						continue;
					}
					int next = g[cur][inds[sp-1]];
					if(!visited[next]){
						ids[sp] = next;
						inds[sp] = 0;
						inds[sp-1]++;
						sp++;
						continue;
					}else if(sp-2 >= 0 && (next != ids[sp-2] || ++parct[sp-1] >= 2)){
						low[cur] = Math.min(low[cur], ord[next]);
					}
					inds[sp-1]++;
				}
			}
		}

		int[] clus = new int[n];
		Arrays.fill(clus, -1);
		int[] q = new int[n];
		int cnum = 0;
		for(int i = 0;i < n;i++){
			if(clus[i] == -1){
				int p = 0;
				q[p++] = i;
				clus[i] = cnum++;
				for(int r = 0;r < p;r++){
					int cur = q[r];
					for(int next : g[cur]){
						if(clus[next] == -1){
							clus[next] = ord[cur] < low[next] ? cnum++ : clus[cur];
							q[p++] = next;
						}
					}
				}
			}
		}
		return clus;
	}


	void run() throws Exception
	{
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);
		
		long s = System.currentTimeMillis();
		solve();
		out.flush();
		if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
//		Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){
//			@Override
//			public void run() {
//				long s = System.currentTimeMillis();
//				solve();
//				out.flush();
//				if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms");
//			}
//		};
//		t.start();
//		t.join();
	}
	
	public static void main(String[] args) throws Exception { new F().run(); }
	
	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;
	
	private int readByte()
	{
		if(lenbuf == -1)throw new InputMismatchException();
		if(ptrbuf >= lenbuf){
			ptrbuf = 0;
			try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
			if(lenbuf <= 0)return -1;
		}
		return inbuf[ptrbuf++];
	}
	
	private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
	private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
	
	private double nd() { return Double.parseDouble(ns()); }
	private char nc() { return (char)skip(); }
	
	private String ns()
	{
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	
	private char[] ns(int n)
	{
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while(p < n && !(isSpaceChar(b))){
			buf[p++] = (char)b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}
	
	private int[] na(int n)
	{
		int[] a = new int[n];
		for(int i = 0;i < n;i++)a[i] = ni();
		return a;
	}
	
	private long[] nal(int n)
	{
		long[] a = new long[n];
		for(int i = 0;i < n;i++)a[i] = nl();
		return a;
	}
	
	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for(int i = 0;i < n;i++)map[i] = ns(m);
		return map;
	}
	
	private int[][] nmi(int n, int m) {
		int[][] map = new int[n][];
		for(int i = 0;i < n;i++)map[i] = na(m);
		return map;
	}
	
	private int ni() { return (int)nl(); }
	
	private long nl()
	{
		long num = 0;
		int b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); }
}
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