[ZJOI2008]树的统计

题意：

题解：

树链剖分模板题，好久没打都忘了

代码：

#include <algorithm>
#include <cstdio>
#include <cstring>
#define lc o << 1
#define rc o << 1 | 1
const int maxn = 60010;
const int inf = 2e9;
int n, a, b, w[maxn], q, u, v;
int cur, h[maxn], nxt[maxn], p[maxn];
int siz[maxn], top[maxn], son[maxn], dep[maxn], fa[maxn], dfn[maxn], rnk[maxn],cnt;
char op[10];
inline void add_edge(int x, int y) {cur++;nxt[cur] = h[x];h[x] = cur;p[cur] = y;
}
struct SegTree {int sum[maxn * 4], maxx[maxn * 4];void build(int o, int l, int r) {if (l == r) {sum[o] = maxx[o] = w[rnk[l]];return;}int mid = (l + r) >> 1;build(lc, l, mid);build(rc, mid + 1, r);sum[o] = sum[lc] + sum[rc];maxx[o] = std::max(maxx[lc], maxx[rc]);}int query1(int o, int l, int r, int ql, int qr) {  // maxif (l > qr || r < ql) return -inf;if (ql <= l && r <= qr) return maxx[o];int mid = (l + r) >> 1;return std::max(query1(lc, l, mid, ql, qr), query1(rc, mid + 1, r, ql, qr));}int query2(int o, int l, int r, int ql, int qr) {  // sumif (l > qr || r < ql) return 0;if (ql <= l && r <= qr) return sum[o];int mid = (l + r) >> 1;return query2(lc, l, mid, ql, qr) + query2(rc, mid + 1, r, ql, qr);}void update(int o, int l, int r, int x, int t) {if (l == r) {maxx[o] = sum[o] = t;return;}int mid = (l + r) >> 1;if (x <= mid)update(lc, l, mid, x, t);elseupdate(rc, mid + 1, r, x, t);sum[o] = sum[lc] + sum[rc];maxx[o] = std::max(maxx[lc], maxx[rc]);}
} st;
void dfs1(int o) {son[o] = -1;siz[o] = 1;for (int j = h[o]; j; j = nxt[j])if (!dep[p[j]]) {dep[p[j]] = dep[o] + 1;fa[p[j]] = o;dfs1(p[j]);siz[o] += siz[p[j]];if (son[o] == -1 || siz[p[j]] > siz[son[o]]) son[o] = p[j];}
}
void dfs2(int o, int t) {top[o] = t;cnt++;dfn[o] = cnt;rnk[cnt] = o;if (son[o] == -1) return;dfs2(son[o], t);for (int j = h[o]; j; j = nxt[j])if (p[j] != son[o] && p[j] != fa[o]) dfs2(p[j], p[j]);
}
int querymax(int x, int y) {int ret = -inf, fx = top[x], fy = top[y];while (fx != fy) {if (dep[fx] >= dep[fy])ret = std::max(ret, st.query1(1, 1, n, dfn[fx], dfn[x])), x = fa[fx];elseret = std::max(ret, st.query1(1, 1, n, dfn[fy], dfn[y])), y = fa[fy];fx = top[x];fy = top[y];}if (dfn[x] < dfn[y])ret = std::max(ret, st.query1(1, 1, n, dfn[x], dfn[y]));elseret = std::max(ret, st.query1(1, 1, n, dfn[y], dfn[x]));return ret;
}
int querysum(int x, int y) {int ret = 0, fx = top[x], fy = top[y];while (fx != fy) {if (dep[fx] >= dep[fy])ret += st.query2(1, 1, n, dfn[fx], dfn[x]), x = fa[fx];elseret += st.query2(1, 1, n, dfn[fy], dfn[y]), y = fa[fy];fx = top[x];fy = top[y];}if (dfn[x] < dfn[y])ret += st.query2(1, 1, n, dfn[x], dfn[y]);elseret += st.query2(1, 1, n, dfn[y], dfn[x]);return ret;
}
int main() {scanf("%d", &n);for (int i = 1; i < n; i++)scanf("%d%d", &a, &b), add_edge(a, b), add_edge(b, a);for (int i = 1; i <= n; i++) scanf("%d", w + i);dep[1] = 1;dfs1(1);dfs2(1, 1);st.build(1, 1, n);scanf("%d", &q);while (q--) {scanf("%s%d%d", op, &u, &v);if (!strcmp(op, "CHANGE")) st.update(1, 1, n, dfn[u], v);if (!strcmp(op, "QMAX")) printf("%d\n", querymax(u, v));if (!strcmp(op, "QSUM")) printf("%d\n", querysum(u, v));}return 0;
}