Submission #239163

#	Time	Username	Problem	Language	Result	Execution time	Memory
239163		crackersamdjam	Dynamic Diameter (CEOI19_diameter)	C++14	49 / 100	5028 ms	117036 KiB

diameter

#pragma GCC optimize("O3")
#pragma GCC target("sse4")

#include <bits/stdc++.h>
#define all(x) (x).begin(), (x).end()
#define gc getchar_unlocked()
#define pc(x) putchar_unlocked(x)
template<typename T> void scan(T &x){x = 0;bool _=0;T c=gc;_=c==45;c=_?gc:c;while(c<48||c>57)c=gc;for(;c<48||c>57;c=gc);for(;c>47&&c<58;c=gc)x=(x<<3)+(x<<1)+(c&15);x=_?-x:x;}
template<typename T> void printn(T n){bool _=0;_=n<0;n=_?-n:n;char snum[65];int i=0;do{snum[i++]=n%10+48;n/= 10;}while(n);--i;if (_)pc(45);while(i>=0)pc(snum[i--]);}
template<typename First, typename ... Ints> void scan(First &arg, Ints&... rest){scan(arg);scan(rest...);}
template<typename T> void print(T n){printn(n);pc(10);}
template<typename First, typename ... Ints> void print(First arg, Ints... rest){printn(arg);pc(32);print(rest...);}

typedef long long ll;
typedef long long T;
constexpr int MM = 1e5+2, LOG = 17;

int n, q, tot, sz[MM], a[MM], b[MM], dep[LOG][MM], in[LOG][MM], out[LOG][MM], t[LOG], centid[LOG][MM], parid[LOG][MM];
ll maxw, c[MM];
std::vector<std::pair<int, ll>> adj[MM];
bool vis[MM];
std::multiset<ll, std::greater<ll>> best, ch[MM];
//all best, ch set for each node as centroid

struct node{
	T val, lp;
	inline void apply(T v){
		val += v;
		lp += v;
	}
};

struct segtree{
#define lc (rt<<1)
#define rc (rt<<1|1)
#define nm ((nl+nr)>>1)
	node tree[MM*3];
	const T DEF = 0;
	//default value
	
	inline void push_up(int rt){
		tree[rt].val = std::max(tree[lc].val, tree[rc].val);
	}
	
	// node with lazy val means yet to push to children (but updated itself)
	inline void push_down(int rt, int nl, int nr){
		T &val = tree[rt].lp;
		if(nl != nr){
			tree[lc].apply(val);
			tree[rc].apply(val);
		}
		val = DEF;
	}
	
	void update(int l, int r, T val, int nl = 1, int nr = n, int rt = 1){
		if(r < nl || l > nr || l > r)
			return;
		if(l <= nl && r >= nr){
			tree[rt].apply(val);
			return;
		}
		push_down(rt, nl, nr);
		update(l, r, val, nl, nm, lc);
		update(l, r, val, nm+1, nr, rc);
		push_up(rt);
	}
	
	T query(int l, int r, int nl = 1, int nr = n, int rt = 1){
		if(r < nl || l > nr || l > r)
			return DEF;
		if(l <= nl && r >= nr)
			return tree[rt].val;
		push_down(rt, nl, nr);
		return std::max(query(l, r, nl, nm, lc), query(l, r, nm+1, nr, rc));
	}
#undef lc
#undef rc
#undef nm
} ST[LOG];

int getsz(int cur, int pre){
	sz[cur] = 1;
	for(auto e: adj[cur]){
		int u = e.first;
		if(u != pre && !vis[u])
			sz[cur] += getsz(u, cur);
	}
	return sz[cur];
}

int findcent(int cur, int pre){
	for(auto e: adj[cur]){
		int u = e.first;
		if(!vis[u] && u != pre && sz[u]*2 > tot)
			return findcent(u, cur);
	}
	return cur;
}

void dfs1(int cur, int pre, int lvl, int cent, ll w){
	in[lvl][cur] = ++t[lvl];
	dep[lvl][cur] = dep[lvl][pre]+1;
	centid[lvl][cur] = cent;
	parid[lvl][cur] = pre == cent ? cur : parid[lvl][pre];
	for(auto u: adj[cur]){
		if(u.first == pre || vis[u.first])
			continue;
		dfs1(u.first, cur, lvl, cent, u.second);
	}
	out[lvl][cur] = t[lvl];
	ST[lvl].update(in[lvl][cur], out[lvl][cur], w);
}

void go(int root, int lvl){
	getsz(root, -1);
	tot = sz[root];
	if(tot == 1)
		return;
	int cent = findcent(root, -1);
	vis[cent] = 1;
	
	dfs1(cent, 0, lvl, cent, 0);
	
	for(auto u: adj[cent]){
		if(vis[u.first])
			continue;
		int st = in[lvl][u.first], ed = out[lvl][u.first];
		ll v = ST[lvl].query(st, ed);
		ch[cent].insert(v);
	}
	while(ch[cent].size() < 2)
		ch[cent].insert(0);
	
	auto ptr = ch[cent].begin();
	best.insert(*ptr + *++ptr);
	
	for(auto u: adj[cent]){
		if(!vis[u.first])
			go(u.first, lvl+1);
	}
}

int main(){
	scan(n, q, maxw);
	for(int i = 0; i < n-1; i++){
		scan(a[i], b[i], c[i]);
		adj[a[i]].emplace_back(b[i], c[i]);
		adj[b[i]].emplace_back(a[i], c[i]);
	}
	
	go(1, 0);
	
	ll d, e, last = 0;
	while(q--){
		scan(d, e);
		d = (d+last)%(n-1);
		e = (e+last)%maxw;
		int aa = a[d], bb = b[d];
		
		ll dif = e-c[d];
		c[d] = e;
		
		for(int i = 0; i < LOG; i++){
			int cent = centid[i][aa];
			if(cent and cent == centid[i][bb]){
				if(dep[i][aa] < dep[i][bb])
					std::swap(aa, bb);
				//aa is deeper, update it
				
				auto ptr = ch[cent].begin();
				best.erase(best.lower_bound(*ptr + *++ptr));
				
				int par = parid[i][aa];
				
				ch[cent].erase(ch[cent].lower_bound(ST[i].query(in[i][par], out[i][par])));
				ST[i].update(in[i][aa], out[i][aa], dif);
				ch[cent].insert(ST[i].query(in[i][par], out[i][par]));
				
				ptr = ch[cent].begin();
				best.insert(*ptr + *++ptr);
			}
		}
		print(last = *best.begin());
	}
}
/*
 * ett each centroid
 * when update edge, loop through LOG levels
 * if for any lvl, there is a point where centid[lvl][a] == centid[lvl][b] != 0, then update the one with higher depth
 * then for its centid, remove old ans from multiset and insert new one
 *
 */

• Subtask 1: 11 / 11
• Subtask 2: 13 / 13
• Subtask 3: 7 / 7
• Subtask 4: 18 / 18
• Subtask 5: 0 / 24
• Subtask 6: 0 / 27