线段树关键函数：void pushup(int u){ tr[u].sum = tr[u << 1].sum + tr[u << 1 | 1].sum;}void build(int u, int l, int r){ if (l == r) tr[u] = {l, r, w[r]}; else { tr[u] = {l, r}; int mid = l + r >> 1; build(u << 1, l, mid), build(u << 1 | 1, mid + 1, r); pushup(u); }}int query(int u, int l, int r){ if (tr[u].l >= l && tr[u].r <= r) return tr[u].sum; int mid = tr[u].l + tr[u].r >> 1; int sum = 0; if (l <= mid) sum = query(u << 1, l, r); if (r > mid) sum += query(u << 1 | 1, l, r); return sum;}void modify(int u, int x, int v){ if (tr[u].l == tr[u].r) tr[u].sum += v; else { int mid = tr[u].l + tr[u].r >> 1; if (x <= mid) modify(u << 1, x, v); else modify(u << 1 | 1, x, v); pushup(u); }}