結果

問題 No.3128 Isosceles Triangle
ユーザー tenten
提出日時 2025-04-30 15:40:46
言語 Java
(openjdk 23)
結果
AC  
実行時間 872 ms / 2,500 ms
コード長 3,502 bytes
コンパイル時間 3,628 ms
コンパイル使用メモリ 88,412 KB
実行使用メモリ 89,588 KB
最終ジャッジ日時 2025-04-30 15:41:06
合計ジャッジ時間 16,523 ms
ジャッジサーバーID
（参考情報） 		judge3 / 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 * 4
other AC * 30
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 # 

import java.io.*;
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) throws Exception {
        FastScanner sc = new FastScanner();
        int n = sc.nextInt();
        TreeMap<Integer, Integer> counts = new TreeMap<>();
        while (n-- > 0) {
            int x = sc.nextInt();
            counts.put(x, counts.getOrDefault(x, 0) + 1);
        }
        TreeMap<Integer, Integer> sums = new TreeMap<>();
        int current = 0;
        for (int x : counts.keySet()) {
            current += counts.get(x);
            sums.put(x, current);
        }
        sums.put(Integer.MIN_VALUE, 0);
        long ans = 0;
        for (int x : counts.keySet()) {
            int num = counts.get(x);
            int target = sums.lowerEntry(x * 2).getValue() - num;
            ans += (num - 1L) * num / 2 * target;
        }
        System.out.println(ans);
    }
}

class FastScanner {
    private DataInputStream din;
    private byte[] buffer;
    private int bufferPointer, bytesRead;
    private static final int BUFFER_SIZE = 1 << 16; // 65,536 バイト

    public FastScanner() {
        din = new DataInputStream(System.in);
        buffer = new byte[BUFFER_SIZE];
        bufferPointer = bytesRead = 0;
    }

    private byte read() {
        try {
            if (bufferPointer == bytesRead) {
                bytesRead = din.read(buffer, 0, BUFFER_SIZE);
                if (bytesRead == -1) return -1;
                bufferPointer = 0;
            }
            return buffer[bufferPointer++];
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    public String next() {
        byte b = read();
        // 空白文字を読み飛ばす
        while (isSpaceChar(b)) {
            b = read();
        }
        StringBuilder sb = new StringBuilder();
        while (!isSpaceChar(b)) {
            sb.append((char) b);
            b = read();
        }
        return sb.toString();
    }

    public int nextInt() {
        int ret = 0;
        byte c = read();
        while (isSpaceChar(c)) c = read();
        boolean neg = (c == '-');
        if (neg) c = read();
        do {
            ret = ret * 10 + c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return neg ? -ret : ret;
    }

    public long nextLong() {
        long ret = 0;
        byte c = read();
        while (isSpaceChar(c)) c = read();
        boolean neg = (c == '-');
        if (neg) c = read();
        do {
            ret = ret * 10L + c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return neg ? -ret : ret;
    }

    public double nextDouble() {
        double ret = 0, div = 1;
        byte c = read();
        while (isSpaceChar(c)) c = read();
        boolean neg = (c == '-');
        if (neg) c = read();
        do {
            ret = ret * 10 + c - '0';
            c = read();
        } while (!isSpaceChar(c) && c != '.');
        if (c == '.') {
            while (!isSpaceChar(c = read())) {
                ret += (c - '0') / (div *= 10);
            }
        }
        return neg ? -ret : ret;
    }

    private boolean isSpaceChar(byte c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }

    public void close() {
        try {
            if (din != null) din.close();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}
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