void up(int p)
{
if (!p) return;
s[p] = s[p * 2] + s[p * 2 + 1];
}
void down(int p, int l, int r)
{
if (col[p])
{
int mid = (l + r) / 2;
s[p * 2] = col[p] * (mid - l + 1);
s[p * 2 + 1] = col[p] * (r - mid);
col[p * 2] = col[p * 2 + 1] = col[p];
col[p] = 0;
}
}
void modify(int p, int l, int r, int x, int y, int c)
{
if (x <= l && r <= y)
{
s[p] = (r - l + 1) * c; //仅修改该结点
col[p] = c; //增加标记,子结点待修改
return;
}
down(p, l, r); //下传lazy标记
int mid = (l + r) / 2;
if (x <= mid) modify(p * 2, l, mid, x, y, c);
if (y > mid) modify(p * 2 + 1, mid + 1, r, x, y, c);
up(p);
}