第一篇题解中

void edit_tree(int x, ll L, ll R, int c) {
	int l = tree[x].l, r = tree[x].r;
	if(X[r + 1] <= L || R <= X[l])
		return;
	if(L <= X[l] && X[r + 1] <= R) {
		tree[x].sum += c;
		pushup(x); //******
		return;
	}
	edit_tree(lson, L, R, c);
	edit_tree(rson, L, R, c);
	pushup(x);
}

打星号的那一行，为啥那里也要pushup？如果没有不是也会在返回之后pushup吗