> 我的邮箱：lazy_p@163.com
上面那份代码有问题，下面是我写的re代码：
import java.math.BigInteger;
import java.util.Scanner;

public class Main {

	private static BigInteger sum = BigInteger.valueOf(0);

	private static void merge(int[] a, int s, int m, int t) {
		int[] tmp = new int[t - s + 1];

		int i = s, j = m, k = 0;
		while (i < m && j <= t) {
			if (a[i] <= a[j]) {
				tmp[k] = a[i];
				k++;
				i++;
			} else {
				tmp[k] = a[j];
				// sum += (j - i) - (j - m);
				sum = sum.add(BigInteger.valueOf((j - i) - (j - m)));
				j++;
				k++;
			}
		}
		while (i < m) {
			tmp[k] = a[i];
			i++;
			k++;
		}

		while (j <= t) {
			tmp[k] = a[j];
			j++;
			k++;
		}

		System.arraycopy(tmp, 0, a, s, tmp.length);
	}

	public static void mergeSort(int[] a, int s, int len) {

		int size = a.length;
		int mid = size / (len << 1);
		int c = size & (len - 1);

		// -------归并到只剩一个有序集合的时候结束算法-------//
		if (mid == 0)
			return;

		// ------进行一趟归并排序-------//
		for (int i = 0; i < mid; ++i) {
			s = i * 2 * len;
			merge(a, s, s + len, (len << 1) + s - 1);
		}

		// -------将剩下的数和倒数一个有序集合归并-------//
		if (c != 0)
			merge(a, size - c - 2 * len, size - c, size - 1);
		//
		// for (int i = 0; i < a.length; ++i) {
		// System.out.print(a[i] + " ");
		// }
		// System.out.println();

		// -------递归执行下一趟归并排序------//
		mergeSort(a, 0, 2 * len);
	}

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		while (true) {
			sum = BigInteger.valueOf(0);
			int size = sc.nextInt();
			if (size == 0)
				break;
			int[] a = new int[size];
			for (int i = 0; i < size; ++i) {
				a[i] = sc.nextInt();
			}
			mergeSort(a, 0, 1);
			System.out.println(sum);
		}

	}

}