Codeforces 588E Duff in the Army 【树链剖分维护区间前k小】
题目链接：Codeforces 588E Duff in the Army
E. Duff in the Army
time limit per test4 seconds
memory limit per test512 megabytes
inputstandard input
outputstandard output
Recently Duff has been a soldier in the army. Malek is her commander.
Their country, Andarz Gu has n cities (numbered from 1 to n) and n - 1 bidirectional roads. Each road connects two different cities. There exist a unique path between any two cities.
There are also m people living in Andarz Gu (numbered from 1 to m). Each person has and ID number. ID number of i - th person is i and he/she lives in city number ci. Note that there may be more than one person in a city, also there may be no people living in the city.
Malek loves to order. That’s why he asks Duff to answer to q queries. In each query, he gives her numbers v, u and a.
To answer a query:
Assume there are x people living in the cities lying on the path from city v to city u. Assume these people’s IDs are p1, p2, …, px in increasing order.
If k = min(x, a), then Duff should tell Malek numbers k, p1, p2, …, pk in this order. In the other words, Malek wants to know a minimums on that path (or less, if there are less than a people).
Duff is very busy at the moment, so she asked you to help her and answer the queries.
Input
The first line of input contains three integers, n, m and q (1 ≤ n, m, q ≤ 105).
The next n - 1 lines contain the roads. Each line contains two integers v and u, endpoints of a road (1 ≤ v, u ≤ n, v ≠ u).
Next line contains m integers c1, c2, …, cm separated by spaces (1 ≤ ci ≤ n for each 1 ≤ i ≤ m).
Next q lines contain the queries. Each of them contains three integers, v, u and a (1 ≤ v, u ≤ n and 1 ≤ a ≤ 10).
Output
For each query, print numbers k, p1, p2, …, pk separated by spaces in one line.
Examples
input
5 4 5
1 3
1 2
1 4
4 5
2 1 4 3
4 5 6
1 5 2
5 5 10
2 3 3
5 3 1
output
1 3
2 2 3
0
3 1 2 4
1 2
Note
Graph of Andarz Gu in the sample case is as follows (ID of people in each city are written next to them):
题意：给定一棵树，每个节点上有若干个编号(1-m)，每个编号只存在一个节点上。有q次查询，问你从u->v的路径上前k小的编号，升序输出。
思路：很自然的想到树链剖分，关键在于维护前10小的编号。我们可以直接归并排序去维护区间前10小的编号，写的又臭又长。。。。。。
AC代码：
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <queue>
#define fi first
#define se second
#define ll o<<1
#define rr o<<1|1
#define CLR(a, b) memset(a, (b), sizeof(a))
using namespace std;
typedef long long LL;
typedef pair<int, int> pii;
const int MOD = 1e9 + 7;
const int MAXN = 1e5 + 10;
void add(LL &x, LL y) { x += y; x %= MOD; }
struct Tree{
int l, r;
int Q[10], cnt;
};
Tree tree[MAXN<<2];
void PushUp(int o) {
int os = 0, ls = tree[ll].cnt, rs = tree[rr].cnt;
int lc = 0, rc = 0;
while(os < 10) {
if(lc < ls && rc < rs) {
if(tree[ll].Q[lc] > tree[rr].Q[rc]) {
tree[o].Q[os++] = tree[rr].Q[rc++];
}
else {
tree[o].Q[os++] = tree[ll].Q[lc++];
}
}
else if(lc < ls) {
tree[o].Q[os++] = tree[ll].Q[lc++];
}
else if(rc < rs) {
tree[o].Q[os++] = tree[rr].Q[rc++];
}
else break;
}
tree[o].cnt = os;
}
priority_queue<int, vector<int>, greater<int> > QQ[MAXN];
void Build(int o, int l, int r)
{
tree[o].l = l; tree[o].r = r;
tree[o].cnt = 0;
if(l == r) {
return ;
}
int mid = (l + r) >> 1;
Build(ll, l, mid); Build(rr, mid+1, r);
}
void Update(int o, int index, int pos) {
if(tree[o].l == tree[o].r) {
int os = 0;
while(!QQ[index].empty() && os < 10) {
tree[o].Q[os++] = QQ[index].top();
QQ[index].pop();
}
tree[o].cnt = os;
return ;
}
int mid = (tree[o].l + tree[o].r) >> 1;
if(pos <= mid) Update(ll, index, pos);
else Update(rr, index, pos);
PushUp(o);
}
int ans[10], ans1[10], res;
void Query(int o, int L, int R)
{
if(tree[o].l == L && tree[o].r == R) {
memcpy(ans1, ans, sizeof(ans));
int os = 0, ls = res, rs = tree[o].cnt;
int lc = 0, rc = 0;
while(os < 10) {
if(lc < ls && rc < rs) {
if(tree[o].Q[rc] > ans1[lc]) {
ans[os++] = ans1[lc++];
}
else {
ans[os++] = tree[o].Q[rc++];
}
}
else if(lc < ls) {
ans[os++] = ans1[lc++];
}
else if(rc < rs) {
ans[os++] = tree[o].Q[rc++];
}
else break;
}
res = os;
return ;
}
int mid = (tree[o].l + tree[o].r) >> 1;
if(R <= mid) Query(ll, L, R);
else if(L > mid) Query(rr, L, R);
else { Query(ll, L, mid), Query(rr, mid+1, R); }
}
struct Edge {
int from, to, next;
};
Edge edge[MAXN<<1];
int head[MAXN], edgenum;
void init() {
edgenum = 0; CLR(head, -1);
}
void addEdge(int u, int v)
{
Edge E = {u, v, head[u]};
edge[edgenum] = E;
head[u] = edgenum++;
}
int son[MAXN], num[MAXN];
int top[MAXN], pos[MAXN], id;
int dep[MAXN], pre[MAXN];
void DFS1(int u, int fa, int d)
{
dep[u] = d; pre[u] = fa; num[u] = 1; son[u] = -1;
for(int i = head[u]; i != -1; i = edge[i].next)
{
int v = edge[i].to;
if(v == fa) continue;
DFS1(v, u, d+1);
num[u] += num[v];
if(son[u] == -1 || num[son[u]] < num[v])
son[u] = v;
}
}
void DFS2(int u, int T)
{
top[u] = T; pos[u] = ++id;
if(son[u] == -1) return ;
DFS2(son[u], T);
for(int i = head[u]; i != -1; i = edge[i].next)
{
int v = edge[i].to;
if(v == pre[u] || v == son[u]) continue;
DFS2(v, v);
}
}
void Solve(int u, int v)
{
int f1 = top[u], f2 = top[v];
res = 0;
while(f1 != f2)
{
if(dep[f1] < dep[f2]) {
swap(u, v); swap(f1, f2);
}
Query(1, pos[f1], pos[u]);
u = pre[f1], f1 = top[u];
}
if(dep[u] > dep[v]) swap(u, v);
Query(1, pos[u], pos[v]);
}
int main()
{
int n, m, q;
while(scanf("%d%d%d", &n, &m, &q) != EOF) {
init();
for(int i = 0; i < n-1; i++) {
int u, v;
scanf("%d%d", &u, &v);
addEdge(u, v); addEdge(v, u);
}
DFS1(1, -1, 1); id = 0; DFS2(1, 1); Build(1, 1, id);
for(int i = 1; i <= m; i++) {
int v; scanf("%d", &v);
if(QQ[v].size() < 10) {
QQ[v].push(i);
}
}
for(int i = 1; i <= n; i++) {
Update(1, i, pos[i]);
}
while(q--) {
int u, v, k; scanf("%d%d%d", &u, &v, &k);
Solve(u, v); int temp = min(k, res);
printf("%d", temp);
for(int i = 0; i < temp; i++) {
printf(" %d", ans[i]);
}
printf("\n");
}
}
return 0;
}