void mergeSort(int q[],int l,int r)
{
//划分区间
    if(l>=r) return ;
    int mid = l + r >> 1;

//组内排序
    mergeSort(q, l , mid);
    mergeSort(q, mid+1 , r);

//合并
    int k = 0 , i = l, j = mid+1;
    while(i <= mid && j <= r)
    {
        if (q[i] <= q[j]) temp[k++] = q[i++];
        else temp[k++] = q[j++];
    }
    while (i <= mid) temp[k++] = q[i++];
    while (j <= r) temp[k++] = q[j++];
    for(i = l, k = 0; i <= r; i++, k++)
        q[l] = temp[k];
}