Codeforces 588E Duff in the Army 【树链剖分维护区间前k小】
2016-04-07 17:21
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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:
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; }
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