POJ3237-Tree （树链剖分，线段树区间更新+点更新+区间查询）

#include <algorithm>
#include <cstring>
#include <cstdio>
#include <iostream>
using namespace std;
const int N = 100005;

//
struct Edge {
    int to, next, cost, id;
} edge[N*2];
int head[N], cntE;
void addedge(int u, int v, int w, int id) {
    edge[cntE].to = v; edge[cntE].next = head[u]; edge[cntE].cost = w; edge[cntE].id = id; head[u] = cntE++;
    edge[cntE].to = u; edge[cntE].next = head[v]; edge[cntE].cost = w; edge[cntE].id = id; head[v] = cntE++;
}
//
int dep[N], sz[N], fa[N], son[N], son_cost[N];
int road[N];
void dfs1(int u, int par, int d) {
    dep[u] = d; sz[u] = 1; fa[u] = par;
    for (int i = head[u]; ~i; i = edge[i].next) {
        int v = edge[i].to;
        if (v != par) {
            road[edge[i].id] = v;
            dfs1(v, u, d+1);
            sz[u] += sz[v];
            if (son[u] == -1 || sz[v] > sz[son[u]]) {
                son[u] = v;
                son_cost[u] = edge[i].cost;
            }
        }
    }
}
int top[N], dfn[N], rk[N], idx;
int a[N];
void dfs2(int u, int rt, int cost) {
    top[u] = rt; dfn[u] = ++idx; a[idx] = cost;
    if (son[u] == -1) return;
    dfs2(son[u], rt, son_cost[u]);
    for (int i = head[u]; ~i; i = edge[i].next) {
        int v = edge[i].to;
        if (v != fa[u] && v != son[u]) dfs2(v, v, edge[i].cost);
    }
}

//
int mx[N<<2], fg[N<<2], mi[N<<2];
#define lson o<<1
#define rson o<<1|1

void pushdown(int o) {
    if (fg[o]) {
        fg[lson] ^= 1;
        fg[rson] ^= 1;
        int tmp = mx[lson];
        mx[lson] = -mi[lson];
        mi[lson] = -tmp;
        tmp = mx[rson];
        mx[rson] = -mi[rson];
        mi[rson] = -tmp;
        fg[o] = 0;
    }
}

void pushup(int o) {
    mx[o] = max(mx[lson], mx[rson]);
    mi[o] = min(mi[lson], mi[rson]);
}

void build(int o, int l, int r) {
    fg[o] = 0;
    if (l == r) {
        mx[o] = a[l];
        mi[o] = a[l];
    } else {
        int mid = (l+r) >> 1;
        build(lson, l, mid);
        build(rson, mid+1, r);
        pushup(o);
    }
}

void CHANGE(int o, int l, int r, int v, int w) {
    if (l == r) {
        mi[o] = mx[o] = w;
    } else {
        pushdown(o);
        int mid = (l + r) >> 1;
        if (mid >= v) CHANGE(lson, l, mid, v, w);
        else CHANGE(rson, mid+1, r, v, w);
        pushup(o);
    }
}

void nega(int o, int l, int r, int L, int R) {
    if (l >= L && r <= R) {
        fg[o] ^= 1;
        int tmp = mx[o];
        mx[o] = -mi[o];
        mi[o] = -tmp;
        return;
    }
    pushdown(o);
    int mid = (l+r) >> 1;
    if (mid >= L) nega(lson, l, mid, L, R);
    if (mid < R) nega(rson, mid+1, r, L, R);
    pushup(o);
}

void NEGATE(int x, int y, int n) {
    while (top[x] != top[y]) {
        if (dep[top[x]] < dep[top[y]]) swap(x, y);
        nega(1, 2, n, dfn[top[x]], dfn[x]);
        x = fa[top[x]];
    }
    if (x == y) return ;
    if (dep[x] > dep[y]) swap(x, y);
    nega(1, 2, n, dfn[son[x]], dfn[y]);
}

int query(int o, int l ,int r, int L, int R) {
    if (l >= L && r <= R) {
        return mx[o];
    }
    pushdown(o);
    int mid = (l+r) >> 1;
    int ans = -(1<<30);
    if (L <= mid) ans = max(ans, query(lson, l, mid, L, R));
    if (R > mid) ans = max(ans, query(rson, mid+1, r, L, R));
    pushup(o);
    return ans;
}

int QUERY(int x, int y, int n) {
    if (x == y) return 0;
    int ans = -(1<<30);
    while (top[x] != top[y]) {
        if (dep[top[x]] < dep[top[y]]) swap(x, y);
        ans = max(ans, query(1, 2, n, dfn[top[x]], dfn[x]));
        x = fa[top[x]];
    }
    if (x == y) return ans;
    if (dep[x] > dep[y]) swap(x, y);
    ans = max(ans, query(1, 2, n, dfn[son[x]], dfn[y])); // 注意这里是son[x]
    return ans;
}

void init() {
    idx = cntE = 0;
    memset(head, -1, sizeof head);
    memset(son, -1, sizeof son);
}

// 区间更新 点更新 区间查询
int main() {
    int n, T;
    scanf("%d",&T);
    int cas = 0;
    while (T--) {
        scanf("%d", &n); init();
        int u, v, w;
        for (int i = 1; i < n; ++i) scanf("%d%d%d", &u, &v, &w), addedge(u, v, w, i);
        dfs1(1, 0, 0); dfs2(1, 1, 0); build(1, 2, n);
        char op[10];
        while (~scanf("%s", op)) {
            if (*op == ‘D‘) break;
            scanf("%d%d", &u, &v);
            if (*op == ‘Q‘) printf("%d\n", QUERY(u, v, n));
            else if (*op == ‘C‘) CHANGE(1, 2, n, dfn[road[u]], v);
            else NEGATE(u, v, n);
        }
    }
    return 0;
}