ACM算法竞赛——归并排序（模板）

void merge_sort(int q[], int l, int r)
{
    if (l >= r) return;

    int mid = l   r >> 1;
    merge_sort(q, l, mid);
    merge_sort(q, mid   1, r);

    int k = 0, i = l, j = mid   1;
    while (i <= mid && j <= r)
        if (q[i] <= q[j]) tmp[k    ] = q[i    ];
        else tmp[k    ] = q[j    ];

    while (i <= mid) tmp[k    ] = q[i    ];
    while (j <= r) tmp[k    ] = q[j    ];

    for (i = l, j = 0; i <= r; i   , j    ) q[i] = tmp[j];
}