結果

問題 No.352 カード並べ
ユーザー yuanyuan-ma921
提出日時 2025-08-29 14:25:50
言語 Java
(openjdk 23)
結果
AC  
実行時間 93 ms / 2,000 ms
コード長 4,887 bytes
コンパイル時間 9,970 ms
コンパイル使用メモリ 83,100 KB
実行使用メモリ 46,620 KB
最終ジャッジ日時 2025-08-29 14:26:02
合計ジャッジ時間 5,210 ms
ジャッジサーバーID
（参考情報） 		judge1 / judge5
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 * 6
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 contest;

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

public class Q750 {
        InputStream is;
        PrintWriter out;
        String INPUT = "";
        
        void solve()
        {
                int n = ni();
                double e = 0;
                for(int i = 1;i <= n;i++){
                        if(i <= 2){
                                e += 1;
                        }else{
                                e += 1. * 2./i;
                                double s = (i-1)*i/2;
                                double s2 = (i-1)*i*(2*i-1)/6;
                                s = (s*s-s2)/2;
                                s = s * 1./((i-2)*(i-1)/2);
                                e += s*(i-2)/i;
                        }
                }
                out.printf("%.14f\n", e);
        }
        
        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");
        }
        
        public static void main(String[] args) throws Exception { new Q750().run(); }
        
        private byte[] inbuf = new byte[1024];
        private 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 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[] na(int n)
        {
                int[] a = new int[n];
                for(int i = 0;i < n;i++)a[i] = ni();
                return a;
        }
        
        private int ni()
        {
                int num = 0, 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 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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