【主席树】 HDOJ 4729 An Easy Problem for Elfness

在树上建立主席树。。。然后如果a>=b，那么就只建边，初始值主席树上查最小值。否则在建一条边或者不建边。不建边的情况下，在主席树上找最小的限制解。。

#include <iostream>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <bitset>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 100005 
#define maxm 200005
#define eps 1e-7
#define mod 1000000007
#define INF 0x3f3f3f3f
#define PI (acos(-1.0))
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
//#define lson o<<1, L, mid 
//#define rson o<<1 | 1, mid+1, R
#define pii pair<int, int>
#pragma comment(linker, "/STACK:16777216")
//typedef long long LL;
//typedef unsigned long long ULL;
//typedef int LL; 
using namespace std;
//LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}
//LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}
// head

#define lson o->ch[0], L, mid
#define rson o->ch[1], mid+1, R
const int LL = 0;
const int RR = 10000;

struct Edge
{
	int v, w;
	Edge *next;
}*H[maxn], *edges, E[maxm];

struct node
{
	int cnt, sum;
	node *ch[2];
}*h[maxn], *tail, pool[maxm << 4];

const int M = 20;
int anc[maxn][M];
int dep[maxn];
int n, m;

void addedges(int u, int v, int w)
{
	edges->v = v;
	edges->w = w;
	edges->next = H[u];
	H[u] = edges++;
}

node* newnode()
{
	tail->cnt = tail->sum = 0;
	tail->ch[0] = tail->ch[1] = NULL;
	return tail++;
}

int to(int u, int d)
{
	for(int i = M - 1; i >= 0; i--) if(dep[anc[u][i]] >= d) u = anc[u][i];
	return u;
}

int lca(int u, int v)
{
	if(dep[u] < dep[v]) swap(u, v);
	u = to(u, dep[v]);
	for(int i = M - 1; i >= 0; i--) if(anc[u][i] != anc[v][i]) u = anc[u][i], v = anc[v][i];
	return u == v ? u : anc[u][0];
}

void init()
{
	tail = pool;
	edges = E;
	memset(H, 0, sizeof H);
}

node* build(int L, int R)
{
	if(L == R) return newnode();
	int mid = (L + R) >> 1;
	node *o = newnode();
	o->ch[0] = build(L, mid);
	o->ch[1] = build(mid+1, R);
	return o;
}

void pushup(node *o)
{
	o->cnt = o->ch[0]->cnt + o->ch[1]->cnt;
	o->sum = o->ch[0]->sum + o->ch[1]->sum;
}

node* update(node* o, int L, int R, int v)
{
	node *p = newnode();
	*p = *o;
	if(L == R) {
		p->cnt++, p->sum += v;
		return p;
	}
	int mid = (L + R) >> 1;
	if(v <= mid) p->ch[0] = update(lson, v);
	else p->ch[1] = update(rson, v);
	pushup(p);
	return p;
}

void dfs(int u, int fa)
{
	anc[u][0] = fa;
	for(Edge *e = H[u]; e; e = e->next) if(e->v != fa) {
		int v = e->v, w = e->w;
		h[v] = update(h[u], LL, RR, w);
		dep[v] = dep[u] + 1;
		dfs(v, u);
	}
}

int query_min(node *a, node *b, node *c, int L, int R)
{
	if(L == R) return L;
	int lcnt = a->ch[0]->cnt + b->ch[0]->cnt - 2 * c->ch[0]->cnt;
	int mid = (L + R) >> 1;
	if(lcnt) return query_min(a->ch[0], b->ch[0], c->ch[0], L, mid);
	else return query_min(a->ch[1], b->ch[1], c->ch[1], mid+1, R);
}

int query(node *a, node *b, node *c, int L, int R, int cnt, int kk)
{
	if(L == R) {
		int t = a->cnt + b->cnt - 2 * c->cnt;
		if(cnt > kk) return L-1;
		else return L + (kk - cnt) / (cnt + t);
	}
	int lcnt = a->ch[0]->cnt + b->ch[0]->cnt - 2 * c->ch[0]->cnt;
	int lsum = a->ch[0]->sum + b->ch[0]->sum - 2 * c->ch[0]->sum;
	int mid = (L + R) >> 1;
	int t = cnt * (mid - L + 1) + lcnt * mid - lsum;
	if(t <= kk) query(a->ch[1], b->ch[1], c->ch[1], mid+1, R, cnt + lcnt, kk - t);
	else return query(a->ch[0], b->ch[0], c->ch[0], L, mid, cnt, kk);
}

void work()
{
	int u, v, w, kk, a, b;
	scanf("%d%d", &n, &m);
	for(int i = 1; i < n; i++) {
		scanf("%d%d%d", &u, &v, &w);
		addedges(u, v, w);
		addedges(v, u, w);
	}

	h[1] = build(LL, RR);
	dfs(1, 1);
	
	for(int i = 1; i < M; i++)
		for(int j = 1; j <= n; j++)
			anc[j][i] = anc[anc[j][i-1]][i-1];

	while(m--) {
		scanf("%d%d%d%d%d", &u, &v, &kk, &a, &b);
		int c = lca(u, v);
		int ans = query_min(h[u], h[v], h[c], LL, RR);
		if(a <= b) {
			ans += kk / a;
			printf("%d\n", ans);
		}
		else {
			int t1 = ans;
			if(kk > a) t1 += 1 + (kk - a) / b;
			int t2 = query(h[u], h[v], h[c], LL, RR, 0, kk / b);
			if(t1 > t2) printf("%d\n", t1);
			else printf("%d\n", t2);
		}
	}
}

int main()
{
	int _;
	scanf("%d", &_);
	for(int i = 1; i <= _; i++) {
		printf("Case #%d:\n", i);
		init();
		work();
	}
	
	
	return 0;
}