题解 | 美妙的约会

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNextInt()) {
            int n = in.nextInt();

            int[] cp = new int[2 * n];
            int[] tag = new int[2 * n];
            long cnt = 0;

            for (int i = 0; i < 2 * n; i++) {
                if (!in.hasNextInt()) return; // 防止读不够数据
                cp[i] = in.nextInt();
                tag[i] = 1;
            }

            for (int i = 0; i < 2 * n; i++) {
                if (tag[i] == 0) continue;

                for (int j = i + 1; j < 2 * n; j++) {
                    if (tag[j] == 1 && cp[j] == cp[i]) {
                        int add = 0;
                        for (int k = i + 1; k < j; k++) {
                            if (tag[k] == 1) add++;
                        }
                        cnt += add;

                        tag[i] = 0;
                        tag[j] = 0;
                        break;
                    }
                }
            }

            System.out.println(cnt);
        }
    }
}