关于线段树合并

int Merge(int x, int y, int l, int r) {
    if (!x) return y;
    if (!y) return x;
    if (l == r) {
        tr[x].cnt |= tr[y].cnt;
        return x;
    }
    int mid = (l + r) >> 1;
    tr[x].ls = Merge(tr[x].ls, tr[y].ls, l, mid);
    tr[x].rs = Merge(tr[x].rs, tr[y].rs, mid + 1, r);
    pushup(x); return x;
}

int Merge(int x, int y, int l, int r) {
    if (!x || !y) {
        tr[++ct] = tr[x + y];
        return ct;
    }
    if (l == r) {
        tr[++ct].cnt = tr[x].cnt | tr[y].cnt;
        return ct;
    }
    int mid = (l + r) >> 1, nd = ++ct;
    tr[nd].ls = Merge(tr[x].ls, tr[y].ls, l, mid);
    tr[nd].rs = Merge(tr[x].rs, tr[y].rs, mid + 1, r);
    pushup(nd); return nd;
}