BZOJ1036

树链剖分的板子题，初学先存一波板子，代码来自点击打开，感谢。

#include <cstdio>#include <cstring>#include <vector>#include <algorithm>using namespace std;const int N = 30005;int dep[N], fa[N], son[N], sz[N], top[N], id[N], idx, val[N];int first[N], nexts[N * 2], vv[N * 2], en;void init() {    en = 0;    idx = 0;    memset(first, -1, sizeof(first));}void add_Edge(int u, int v) {    vv[en] = v;    nexts[en] = first[u];    first[u] = en++;}void dfs1(int u, int f, int d) {    dep[u] = d;    sz[u] = 1;    fa[u] = f;    son[u] = 0;    for (int i = first[u]; i + 1; i = nexts[i]) {        int v = vv[i];        if (v == f) continue;        dfs1(v, u, d + 1);        sz[u] += sz[v];        if (sz[son[u]] < sz[v])            son[u] = v;    }}void dfs2(int u, int tp) {    id[u] = ++idx;    top[u] = tp;    if (son[u]) dfs2(son[u], tp);    for (int i = first[u]; i + 1; i = nexts[i]) {        int v = vv[i];        if (v == fa[u] || v == son[u]) continue;        dfs2(v, v);    }}const int INF = 0x3f3f3f3f;int n;#define lson(x) ((x<<1)+1)#define rson(x) ((x<<1)+2)struct Node {    int l, r, maxx, sum;} node[N * 4];void pushup(int x) {    node[x].maxx = max(node[lson(x)].maxx, node[rson(x)].maxx);    node[x].sum = node[lson(x)].sum + node[rson(x)].sum;}void build(int l, int r, int x = 0) {    node[x].l = l; node[x].r = r;    if (l == r) {        node[x].maxx = node[x].sum = val[l];        return;    }    int mid = (l + r) / 2;    build(l, mid, lson(x));    build(mid + 1, r, rson(x));    pushup(x);}void add(int v, int val, int x = 0) {    if (node[x].l == node[x].r) {        node[x].sum = node[x].maxx = val;        return;    }    int mid = (node[x].l + node[x].r) / 2;    if (v <= mid) add(v, val, lson(x));    if (v > mid) add(v, val, rson(x));    pushup(x);}int query(int l, int r, int ty, int x = 0) {    if (node[x].l >= l && node[x].r <= r) {        if (ty) return node[x].sum;        return node[x].maxx;    }    int mid = (node[x].l + node[x].r) / 2;    int ans = -INF, tmp;    if (ty) ans = 0;    if (l <= mid) {        tmp = query(l, r, ty, lson(x));        if (ty) ans += tmp;        else ans = max(ans, tmp);    }    if (r > mid) {        tmp = query(l, r, ty, rson(x));        if (ty) ans += tmp;        else ans = max(ans, tmp);    }    return ans;}int gao(int u, int v, int ty) {    int ans = -INF, tmp; if (ty) ans = 0;    int tp1 = top[u], tp2 = top[v];    while (tp1 != tp2) {        if (dep[tp1] < dep[tp2]) {            swap(tp1, tp2);            swap(u, v);        }        tmp = query(id[tp1], id[u], ty);        if (ty) ans += tmp;        else ans = max(ans, tmp);        u = fa[tp1];        tp1 = top[u];    }    if (dep[u] > dep[v]) swap(u, v);    tmp = query(id[u], id[v], ty);    if (ty) ans += tmp;    else ans = max(ans, tmp);    return ans;}int main() {    while (~scanf("%d", &n)) {        init();        int u, v;        for (int i = 1; i < n; i++) {            scanf("%d%d", &u, &v);            add_Edge(u, v);            add_Edge(v, u);        }        dfs1(1, 0, 1);        dfs2(1, 1);        for (int i = 1; i <= n; i++) scanf("%d", &val[id[i]]);        build(1, idx);        int q;        char Q[10]; int a, b;        scanf("%d", &q);        while (q--) {            scanf("%s%d%d", Q, &a, &b);            if (Q[0] == 'C') add(id[a], b);            else {                int ty = 0;                if (Q[1] == 'S') ty = 1;                printf("%d\n", gao(a, b, ty));            }        }    }    return 0;}