【TOJ 3701.】A Pungent Problem【树链刨分】

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裸的树链刨分。可以当做入门题，或者splay也可以做
#include <cstdio>#include <cstring>#include <vector>#include <algorithm>using namespace std;#define N 30009#define lc (d<<1)#define rc (d<<1|1)#define mid (l+r>>1)#define inf 0x3f3f3f3fstruct Tr{    int mx, sum;}tr[N<<4];int n, sun[N], tid[N], top[N], val[N], dep[N], tot, tmp[N], fa[N];vector<int>V[N];int dfs(int u, int f) {    int i, v, id = u, mx = 0, c = 1;    fa[u] = f;    for (i = 0;i < V[u].size();i++) {        v = V[u][i];        if (v == f) continue;        int tm = dfs(v, u);        if (tm > mx) mx = tm, id = v;        c += tm;    }    sun[u] = id;    return c;}void dfs1(int u, int d, int Top) {    int i, v;    dep[u] = d, tid[u] = ++tot, top[u] = Top;    if (tid[sun[u]] == -1) dfs1(sun[u], d+1, Top);    for (i = 0;i < V[u].size();i++) {        v = V[u][i];        if (tid[v] != -1) continue;        dfs1(v, d+1, v);    }}void Push(int d) {    tr[d].sum = tr[lc].sum+tr[rc].sum;    tr[d].mx = max(tr[lc].mx, tr[rc].mx);}void build(int d, int l, int r) {    if (l == r) {        tr[d].mx = tr[d].sum = val[l];        return;    }    build(lc, l, mid), build(rc, mid+1, r);    Push(d);}void update(int d, int l, int r, int pos, int v) {    if (l == r && pos == l) {        tr[d].mx = tr[d].sum = v;        return;    }    if (pos <= mid) update(lc, l, mid, pos, v);    else update(rc, mid+1, r, pos, v);    Push(d);}int query(int d, int l, int r, int L, int R, int k) {    if (l == L && r == R) {        if (k) return tr[d].mx;        return tr[d].sum;    }    if (R <= mid) return query(lc, l, mid, L, R, k);    else if (L > mid) return query(rc, mid+1, r, L, R, k);    else {        if (k) return max(query(lc, l, mid, L, mid, k), query(rc, mid+1, r, mid+1, R, k));        else return query(lc, l, mid, L, mid, k)+query(rc, mid+1, r, mid+1, R, k);    }}int M(int u, int v, int k) {    int re = 0, tm;    if (k) re = -inf;    while (top[u] != top[v]) {        if (dep[top[u]] < dep[top[v]]) swap(u, v);        tm = query(1, 1, tot, tid[top[u]], tid[u], k);        if (k) re = max(tm, re);        else re += tm;        u = fa[top[u]];    }    if (tid[u] > tid[v]) swap(u, v);    tm = query(1, 1, tot, tid[u], tid[v], k);    if (k) re = max(tm, re);    else re += tm;    return re;}int main() {    int i, j, u, v, m;    char w[10];    while (~scanf("%d", &n)) {        for (i = 1;i <= n;i++) V[i].clear();        for (i = 1;i < n;i++) {            scanf("%d%d", &u, &v);            V[u].push_back(v), V[v].push_back(u);        }        memset(tid, -1, sizeof(tid));        tot = 0;        for (i = 1;i <= n;i++) scanf("%d", &tmp[i]);        dfs(1, -1);        dfs1(1, 0, 1);        for (i = 1;i <= n;i++) val[tid[i]] = tmp[i];        build(1, 1, tot);        scanf("%d", &m);        while (m--) {            scanf("%s%d%d", w, &u, &v);            if (w[0] == 'C') {                update(1, 1, tot, tid[u], v);            }else if (w[1] == 'M') {                printf("%d\n", M(u, v, 1));            }else printf("%d\n", M(u, v, 0));        }    }}
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