luogu P4115 Qtree4

题目链接

luogu P4115 Qtree4

题解

动态点分治,和上一题一样.同样三个堆.就是带权，用边权替换深度就好

为什么要单独写这个题解呢，因为我卡常卡了一天....据说树剖比rmq快？ 在第24次AC

同样也有更有做法

代码

#include<queue>
#include<cstdio>
#include<cctype>
#include<algorithm>

/*char ch;
char buf[100000],*p1 = buf,*p2 = buf;
int F = 1;
#define nc() \
    p1 == p2 && (p2 = (p1 = buf) + fread(buf,1,100000,stdin),p1 == p2) ? EOF :*p1 ++;
#define read(x)  \
    x = 0;ch = nc();F = 1; \
    while(!isdigit(ch)) { if (ch == '-') F = -1; ch = nc();}\
    while(isdigit(ch))x = x*10+ch - '0',ch = nc();\
    x *= F;
    */

#define gc() (SS==TT&&(TT=(SS=IN)+fread(IN,1,MAXIN,stdin),SS==TT)?EOF:*SS++)
const int MAXIN=3e5;
char IN[MAXIN],*SS=IN,*TT=IN;
#define gc() (SS==TT&&(TT=(SS=IN)+fread(IN,1,MAXIN,stdin),SS==TT)?EOF:*SS++)
inline int read() {
    int now=0,f=1;register char c=gc();
    for(;!isdigit(c);c=gc()) if(c=='-') f=-1;
    for(;isdigit(c);now=now*10+c-'0',c=gc());
    return now*f;
} 

#define INF 998244353
const int maxn = 100007;  

int son[maxn],f[maxn],mn[maxn << 1][25],root,tot;
struct node {
    int u,v,next,w;
} edge[maxn << 1];
int head[maxn],num = 0;
inline void add_edge(int u,int v,int w) {
    edge[++ num].v = v;edge[num].next = head[u];head[u] = num;
    edge[num].w = w;
}
int n;
int lg[maxn << 1],dfn;// = 0;
bool col[maxn]; 

struct Heap {
    std::priority_queue<int>A,B;
    inline void push(int x) { A.push(x); }
    inline void erase(int x) { B.push(x); }
    inline void pop() { while(B.size() && A.top() == B.top())  A.pop(),B.pop();	A.pop();  }
    inline int top() {
        while(B.size() && A.top() == B.top()) A.pop(),B.pop();
        return A.top();
    }
    inline int size() { return A.size() - B.size();  }
    int retop() { if(size() < 2) return 0;int x = top();pop();int ret = top();push(x);return ret;}
} b[maxn],c[maxn],ans;
inline void insert(Heap &s) {if(s.size() > 1)ans.push(s.top() + s.retop());}
inline void dele(Heap &s) {if(s.size() > 1) ans.erase(s.top() + s.retop());} 

int pos[maxn],Dis[maxn];
int id[maxn],tm;  

void dfs_rmq (int x,int fa) {
    int t = ++ tm; mn[pos[x] = ++ dfn][0] = tm,id[t] = x;
    for(int i = head[x];i;i = edge[i].next) {
        int v = edge[i].v;
        if(v == fa)continue;
        Dis[v] = Dis[x] + edge[i].w;
        dfs_rmq(v,x);
        mn[++ dfn][0] = t; //访问完子树后加上Qwq
    }
}
inline int lca(int x,int y) {
    x = pos[x];y = pos[y];
    if(y < x) std::swap(x,y);
    int k = lg[y - x + 1];
    return id[std::min(mn[x][k],mn[y - (1 << k) + 1][k])];
}
inline int dis(int x,int y) {
    return Dis[x] + Dis[y] - 2 * Dis[lca(x,y)];
}
bool vis[maxn];int fa[maxn];
void get_root(int x,int fa) {
    son[x] = 1; f[x] = 0;
    for(int i = head[x];i;i = edge[i].next) {
        int v = edge[i].v;
        if(v == fa || vis[v]) continue;
        get_root(v,x);
        son[x] += son[v];f[x] = std::max(f[x],son[v]);
    }
    f[x] = std::max(f[x],tot - son[x]);
    if(f[x] < f[root]) root = x;
}
void get(int x,int Fa,int rt) {
    b[root].push(dis(x,fa[root]));
    for(int i = head[x];i;i = edge[i].next) {
        int v = edge[i].v; if(v == Fa || vis[v]) continue;
        get(v,x,rt);
    }
}
void build(int x,int Fa) {
    fa[x] = Fa;vis[x] = 1;
    c[x].push(0);
    get(x,0,Fa);
    for(int i = head[x];i;i = edge[i].next) {
        int v = edge[i].v;
        if(!vis[v] && v != Fa) {
            tot = son[edge[i].v];root = 0;f[0] = INF;
            get_root(edge[i].v,x);
            v = root;
            build(root,x);
            c[x].push(b[v].top());
        }
    }
    insert(c[x]);
}
void turn(int x,bool type) {
    dele(c[x]);
    if(type) c[x].erase(0);
    else c[x].push(0);
    insert(c[x]);
    for(int i = x;i;i = fa[i]) {
        dele(c[fa[i]]);
        //printf("%d ",i);
        if(b[i].size())	c[fa[i]].erase(b[i].top());
        if(type)b[i].erase(dis(x,fa[i])); else b[i].push(dis(x,fa[i]));
        if(b[i].size()) c[fa[i]].push(b[i].top());
        insert(c[fa[i]]);
    }
    //puts("");
} 

inline char get(){
    char c=gc();
    while(c!='A'&&c!='C') c=gc();
    return c;
}
int main() {
     n = read();
     //read(n);
     for(int u,v,w,i = 1;i < n;++ i) {
        u = read(),v = read(),w = read();
        //read(u);read(v);read(w);
        add_edge(u,v,w);add_edge(v,u,w);
    }
    dfs_rmq(1,0);
    for(int i = 2;i <= dfn;++ i) lg[i] = lg[i >> 1] + 1;
    for(int i = 1;i <= lg[dfn];++ i)
  		for(int j = dfn - (1 << i - 1);j;-- j)
  			mn[j][i] = std::min(mn[j][i - 1],mn[j + (1 << i - 1)][i - 1]);
  	f[0] = INF; root = 0; tot = n;
    get_root(1,0);
    build(root,0);
    //char opt[10];
    int Q = read(); 

    int sum = n;
    for(int asd;Q --;) {
        //scanf("%s",opt + 1);
        if(get() == 'C') {
            asd = read();//read(asd);
            if(col[asd]) turn(asd,0), sum ++,col[asd] = 0;
            else turn(asd,1),sum --,col[asd] = 1;
        }
        else  {
            if(sum == 1)puts("0");
            else if(!sum)puts("They have disappeared.");
            else printf("%d\n",std::max(0,ans.top()));
        }
    }
    return 0;
}