二维树状数组模板

int Lowbit(int t)
{
    return t&(-t);
}
void add(int x, int y)
{
    int i=y;
    while(x<=n)
    {
        y=i;
        while(y<=n)
        {
            c[x][y]++;
            y+=Lowbit(y);
        }
        x+=Lowbit(x);
    }
}
int Sum(int x, int y)
{
    int i=y, sum=0;
    while(x>0)
    {
        y=i;
        while(y>0)
        {
            sum+=c[x][y];
            y-=Lowbit(y);
        }
        x-=Lowbit(x);
    }
    return sum;
}