树链剖分+线段树 poj3237 Tree

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题意：3种操作，1单点更新，2路径正负反转，3路径查询最大值

思路：线段树维护最大值和最小值和一个懒惰标记，然后在线段树的基础上用树链剖分维护

#include<map>#include<set>#include<cmath>#include<ctime>#include<stack>#include<queue>#include<cstdio>#include<cctype>#include<string>#include<vector>#include<cstring>#include<iostream>#include<algorithm>#include<functional>#define fuck(x) cout<<"["<<x<<"]"#define FIN freopen("input.txt","r",stdin)#define FOUT freopen("output.txt","w+",stdout)using namespace std;typedef long long LL;#define lson l,m,rt<<1#define rson m+1,r,rt<<1|1const int MX = 1e4 + 5;const int INF = 0x3f3f3f3f;struct Edge {    int u, v, nxt, cost;} E[MX << 2];int Head[MX], h_r;void edge_init() {    h_r = 0;    memset(Head, -1, sizeof(Head));}void edge_add(int u, int v, int cost) {    E[h_r].v = v; E[h_r].u = u; E[h_r].cost = cost;    E[h_r].nxt = Head[u];    Head[u] = h_r++;}int MAX[MX << 2], MIN[MX << 2], col[MX << 2], A[MX];void push_up(int rt) {    MAX[rt] = max(MAX[rt << 1], MAX[rt << 1 | 1]);    MIN[rt] = min(MIN[rt << 1], MIN[rt << 1 | 1]);}void change(int rt) {    swap(MAX[rt], MIN[rt]);    MAX[rt] = -MAX[rt];    MIN[rt] = -MIN[rt];}void push_down(int rt) {    if(col[rt]) {        col[rt << 1] ^= 1;        col[rt << 1 | 1] ^= 1;        change(rt << 1); change(rt << 1 | 1);        col[rt] = 0;    }}void build(int l, int r, int rt) {    col[rt] = 0;    if(l == r) {        MAX[rt] = MIN[rt] = A[l];        return;    }    int m = (l + r) >> 1;    build(lson);    build(rson);    push_up(rt);}void update_seg(int L, int R, int l, int r, int rt) {    if(L <= l && r <= R) {        change(rt);        col[rt] ^= 1;        return;    }    int m = (l + r) >> 1;    push_down(rt);    if(L <= m) update_seg(L, R, lson);    if(R > m) update_seg(L, R, rson);    push_up(rt);}void update(int x, int d, int l, int r, int rt) {    if(l == r) {        MAX[rt] = MIN[rt] = d;        return;    }    int m = (l + r) >> 1;    push_down(rt);    if(x <= m) update(x, d, lson);    else update(x, d, rson);    push_up(rt);}int query(int L, int R, int l, int r, int rt) {    if(L <= l && r <= R) {        return MAX[rt];    }    int m = (l + r) >> 1, ret = -INF;    push_down(rt);    if(L <= m) ret = max(ret, query(L, R, lson));    if(R > m) ret = max(ret, query(L, R, rson));    return ret;}int fa[MX], top[MX], siz[MX], son[MX], dep[MX], id[MX], rear;void DFS1(int u, int f, int d) {    fa[u] = f; dep[u] = d;    son[u] = 0; siz[u] = 1;    for(int i = Head[u]; ~i; i = E[i].nxt) {        int v = E[i].v;        if(v == f) continue;        DFS1(v, u, d + 1);        siz[u] += siz[v];        if(siz[son[u]] < siz[v]) {            son[u] = v;        }    }}void DFS2(int u, int tp) {    top[u] = tp;    id[u] = ++rear;    if(son[u]) DFS2(son[u], tp);    for(int i = Head[u]; ~i; i = E[i].nxt) {        int v = E[i].v;        if(v == fa[u] || v == son[u]) continue;        DFS2(v, v);    }}/*节点1不使用，建树要小心一般边使用更深的那个点的id编号来表示*/void HLD_presolve() {    rear = 0;    DFS1(1, 0, 1);    DFS2(1, 1);    for(int i = 0; i < 2 * (rear - 1); i += 2) {        int u = E[i].u, v = E[i].v;        if(dep[u] < dep[v]) swap(u, v);        A[id[u]] = E[i].cost;    }    A[1] = -INF;    build(1, rear, 1);}/*找到对应边的更深的点的id编号*/void HLD_update(int x, int d) {    x = (x - 1) * 2;    int u = E[x].u, v = E[x].v;    if(dep[u] < dep[v]) swap(u, v);    update(id[u], d, 1, rear, 1);}/*注意最后一个查询与单点更新的区别以及u==v就需要返回x*/void HLD_negate(int u, int v) {    int tp1 = top[u], tp2 = top[v];    while(tp1 != tp2) {        if(dep[tp1] < dep[tp2]) {            swap(u, v);            swap(tp1, tp2);        }        update_seg(id[tp1], id[u], 1, rear, 1);        u = fa[tp1]; tp1 = top[u];    }    if(u == v) return;    if(dep[u] > dep[v]) swap(u, v);    update_seg(id[son[u]], id[v], 1, rear, 1);}int HLD_query(int u, int v) {    int tp1 = top[u], tp2 = top[v], ans = -INF;    while(tp1 != tp2) {        if(dep[tp1] < dep[tp2]) {            swap(u, v);            swap(tp1, tp2);        }        ans = max(ans, query(id[tp1], id[u], 1, rear, 1));        u = fa[tp1]; tp1 = top[u];    }    if(u == v) return ans;    if(dep[u] > dep[v]) swap(u, v);    ans = max(ans, query(id[son[u]], id[v], 1, rear, 1));    return ans;}int main() {    int T, n; //FIN;    scanf("%d", &T);    while(T--) {        edge_init();        scanf("%d", &n);        for(int i = 1; i <= n - 1; i++) {            int u, v, cost;            scanf("%d%d%d", &u, &v, &cost);            edge_add(u, v, cost);            edge_add(v, u, cost);        }        HLD_presolve();        char op[10]; int a, b;        while(scanf("%s", op), op[0] != 'D') {            scanf("%d%d", &a, &b);            if(op[0] == 'Q') printf("%d\n", HLD_query(a, b));            else if(op[0] == 'C') HLD_update(a, b);            else HLD_negate(a, b);        }    }    return 0;}