結果

問題 No.947 ABC包囲網
コンテスト
ユーザー uwi
提出日時 2020-01-05 04:44:05
言語 Java
(openjdk 23)
結果
AC  
実行時間 84 ms / 2,000 ms
コード長 4,920 bytes
コンパイル時間 3,980 ms
コンパイル使用メモリ 87,588 KB
実行使用メモリ 38,348 KB
最終ジャッジ日時 2024-11-22 21:54:39
合計ジャッジ時間 9,165 ms
ジャッジサーバーID
（参考情報） 		judge5 / judge2
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ファイルパターン 結果
other AC * 60
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ソースコード

diff # 

package adv2019;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Comparator;
import java.util.InputMismatchException;

public class D10_5 {
	InputStream is;
	PrintWriter out;
	String INPUT = ""; 
	
	void solve()
	{
		int n = ni();
		int[][] co = new int[n][];
		for(int i = 0;i < n;i++) {
			co[i] = na(2);
		}
		out.println(countTrianglesContainingOX(co));
	}
	
	public static long countTrianglesContainingO(int[][] co)
	{
		int n = co.length;
		Arrays.sort(co, compArgi);

		long ret = (long)n*(n-1)*(n-2)/6;
		for(int h = 0, t = 0, hm = 0, tm = 0;h < 2*n;h++, hm++) {
			if(hm == n)hm = 0;
			while(t < h && cross(co[hm], co[tm]) > 0) {
				if(++tm == n)tm = 0;
				t++;
			}
			if(h >= n)ret -= (long)(h-t)*(h-t-1)/2;
		}
		return ret;
	}
	
	public static long countTrianglesContainingOX(int[][] co)
	{
		int n = co.length;
		Arrays.sort(co, compArgi);

		long ret = (long)n*(n-1)*(n-2)/6;
		long sameline = 0;
		for(int h = 0, t = 0, t2 = 0, hm = 0, tm = 0, t2m = 0;h < 2*n;h++, hm++) {
			if(hm == n)hm = 0;
			while(t < h && (t <= h-n || cross(co[hm], co[tm]) > 0 || cross(co[hm], co[tm]) == 0 && dot(co[hm], co[tm]) > 0 && tm > hm)) {
				if(++tm == n)tm = 0;
				t++;
			}
			while(t2 < h && (t2 <= h-n || cross(co[hm], co[t2m]) > 0 || cross(co[hm], co[t2m]) == 0 && (dot(co[hm], co[t2m]) > 0 && t2m > hm || dot(co[hm], co[t2m]) < 0))) {
				if(++t2m == n)t2m = 0;
				t2++;
			}
			if(h >= n) {
				ret -= (long)(h-t)*(h-t-1)/2 - (t2-t)*(t2-t-1)/2;
			}
		}
		return ret + sameline;
	}
	
	public static long dot(int[] a, int[] b){ return (long)a[0]*b[0]+(long)a[1]*b[1]; }
	public static long cross(int[] a, int[] b){ return (long)a[0]*b[1]-(long)a[1]*b[0];	}

	
	public static Comparator<int[]> compArgi = new Comparator<int[]>(){
		public int compare(int[] a, int[] b)
		{
			long ax = a[0], ay = a[1];
			long bx = b[0], by = b[1];
			int za = ay > 0 || ay == 0 && ax > 0 ? 0 : 1;
			int zb = by > 0 || by == 0 && bx > 0 ? 0 : 1;
			if(za != zb)return za - zb;
			if(ay*bx-ax*by != 0)return Long.signum(ay*bx-ax*by);
			return Long.signum((ax*ax+ay*ay)-(bx*bx+by*by));
		}
	};

	
	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 D10_5().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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