#514422 (Java) No.1115 二つの数列 / Two Sequences

• 問題: No.1115 二つの数列 / Two Sequences
• ユーザー: sca1l
• 提出日時: 2020-07-19 14:06:28
• 言語: Java (openjdk 23)
• 結果: AC
• 実行時間: 689 ms / 2,000 ms
• コード長: 2,095 bytes
• コンパイル時間: 4,191 ms
• コンパイル使用メモリ: 85,752 KB
• 実行使用メモリ: 52,492 KB
• 最終ジャッジ日時: 2024-12-16 05:48:07
• 合計ジャッジ時間: 19,472 ms
• ジャッジサーバーID （参考情報）: judge1 / judge2

ファイルパターン	結果
sample	AC * 5
other	AC * 35

ソースコード

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import java.util.*;
public class Main{
    
    static final int MOD = (int)1e9+7;
    static HashMap<Integer, Integer> memo;
    
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] a = new int[n];
        for(int i=0; i<n; i++){
            a[i] = Integer.parseInt(sc.next());
        }
        int[] b = new int[n+1];
        for(int i=0; i<n; i++){
            int idx = Integer.parseInt(sc.next());
            b[idx] = i;
        }
        
        int[] c = new int[n];
        for(int i=0; i<n; i++){
            c[i] = b[a[i]]+1;
        }
        
        Inversion inv = new Inversion();
        long ans = inv.inv(c);
        
        System.out.println(ans);
    }
}
class Inversion{
    public long inv(int[] a){
        long cnt = 0;
        int size = a.length;
        BinaryIndexedTree bit = new BinaryIndexedTree(size);
        
        for(int i=0; i<size; i++){
            int p = a[i];
            bit.add(p, 1);
            cnt += i + 1 - bit.sum(p);
        }
        return cnt;
    }
    
    //座圧(1-indexed)
    //使うとよい
    public static int[] shrink(int[] a){
        int n = a.length;
        long[] b = new long[n];
        for (int i = 0; i < n; i++){
            b[i] = ((long)a[i] << 32) + i;
        }
        Arrays.sort(b);
        int[] ret = new int[n];
        int p = 1;//1-indexed
        for (int i = 0; i < n; i++){
            if (i > 0 && (b[i]>>32) != (b[i - 1]>>32)){
                p++;
            }
            ret[(int)(b[i]>>32)] = p;
        }
        return ret;
    }
}
class BinaryIndexedTree{
    int size;
    long[] tree;
    
    public BinaryIndexedTree(int n){
        this.size = n;
        this.tree = new long[n+1];
    }
    
    public long sum(int i){
        long s = 0L;
        while(0<i){
            s += tree[i];
            i -= i & -i;
        }
        return s;
    }
    
    public void add(int i, int x){
        while(i<=size){
            tree[i] += x;
            i += i & -i;
        }
    }
}
 
 
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