提出 #74704742

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ソースコード 拡げる

import java.io.*;
import java.util.StringTokenizer;

public class Main {
    static class BinaryIndexedTree {
        int size;
        long[] array;
        public BinaryIndexedTree(int size) {
            this.size = size;
            array = new long[size + 1];
        }
        public void update(int idx, int val) {
            for (idx++; idx <= size; idx += idx & -idx) {
                array[idx] += val;
            }
        }
        public long query(int idx) {
            long sum = 0;
            for (idx++; idx > 0; idx -= idx & -idx) {
                sum += array[idx];
            }
            return sum;
        }
        public long query(int lef, int rig) {
            if (lef > rig) return 0;
            return query(rig) - query(lef - 1);
        }
    }
    public static void main(String[] args) {
        InputReader reader = new InputReader(System.in);
        PrintWriter writer = new PrintWriter(System.out, false);
        int N = reader.nextInt();
        int K = reader.nextInt();
        int[] A = new int[N];
        for (int i = 0; i < N; i++) {
            A[i] = reader.nextInt();
        }
        writer.println(countAtMost(A, K) - countAtMost(A, K - 1));
        writer.close();
        System.exit(0);
    }

    private static long countAtMost(int[] A, int K) {
        if (K < 0) return 0;
        int N = A.length;
        long result = 0, inversion = 0;
        BinaryIndexedTree binaryIndexedTree = new BinaryIndexedTree(N + 1);
        for (int r = 0, l = 0; r < N; r++) {
            inversion += binaryIndexedTree.query(A[r] + 1, N);
            binaryIndexedTree.update(A[r], 1);
            while (inversion > K) {
                inversion -= binaryIndexedTree.query(A[l] - 1);
                binaryIndexedTree.update(A[l++], -1);
            }
            result += r - l + 1;
        }
        return result;
    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;
        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }
        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }
        public int nextInt() {
            return Integer.parseInt(next());
        }
        public long nextLong() {
            return Long.parseLong(next());
        }
        public double nextDouble() {
            return Double.parseDouble(next());
        }
        public String nextLine() {
            String str = "";
            try {
                str = reader.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }
}

提出情報

ジャッジ結果