Codeforces 343D Water Tree

本文介绍了一种使用两个数组表示树状结构的方法,并通过一系列操作来模拟水填充过程。该方法利用了离线查询和区间更新的思想,适用于解决涉及树形结构的动态变化问题。

Mad scientist Mike has constructed a rooted tree, which consists of n vertices. Each vertex is a reservoir which can be either empty or filled with water.

The vertices of the tree are numbered from 1 to n with the root at vertex 1. For each vertex, the reservoirs of its children are located below the reservoir of this vertex, and the vertex is connected with each of the children by a pipe through which water can flow downwards.

Mike wants to do the following operations with the tree:

  1. Fill vertex v with water. Then v and all its children are filled with water.
  2. Empty vertex v. Then v and all its ancestors are emptied.
  3. Determine whether vertex v is filled with water at the moment.
Initially all vertices of the tree are empty.

Mike has already compiled a full list of operations that he wants to perform in order. Before experimenting with the tree Mike decided to run the list through a simulation. Help Mike determine what results will he get after performing all the operations.

Input

The first line of the input contains an integer n (1 ≤ n ≤ 500000) — the number of vertices in the tree. Each of the following n - 1 lines contains two space-separated numbers ai, bi (1 ≤ ai, bi ≤ n, ai ≠ bi) — the edges of the tree.

The next line contains a number q (1 ≤ q ≤ 500000) — the number of operations to perform. Each of the following q lines contains two space-separated numbers ci (1 ≤ ci ≤ 3), vi (1 ≤ vi ≤ n), where ci is the operation type (according to the numbering given in the statement), and vi is the vertex on which the operation is performed.

It is guaranteed that the given graph is a tree.

Output

For each type 3 operation print 1 on a separate line if the vertex is full, and 0 if the vertex is empty. Print the answers to queries in the order in which the queries are given in the input.

Sample test(s)
Input
5
1 2
5 1
2 3
4 2
12
1 1
2 3
3 1
3 2
3 3
3 4
1 2
2 4
3 1
3 3
3 4
3 5
Output
0
0
0
1
0
1
0
1

感觉好神奇的方法,用俩数组表示出一棵树;

#include <bits/stdc++.h>
using namespace std;
const int mx = 5e5 + 5;

vector<int> g[mx];
set<int> Empty;
int L[mx], R[mx], fa[mx];
int timer, to;

void dfs(int v, int p = -1)
{
    L[v] = ++timer;
    for (int i = 0; i < g[v].size(); ++i)
        if ((to = g[v][i]) != p)
            fa[to] = v, dfs(to, v);
    R[v] = timer;
    if (R[v] == L[v]) Empty.insert(L[v]);
}

bool empty(int v)
{
    set<int>::iterator it = Empty.lower_bound(L[v]);
    return it != Empty.end() && *it <= R[v];
}

void display()
{
	set<int>::const_iterator p;
	for (p = Empty.begin(); p != Empty.end(); ++p)
	        cout << *p << " ";
	    cout << "\n";	
}

int main()
{
    int n, q, a, b, op, v;
    scanf("%d", &n);
    for(int i=1;i<n;i++)
    {
        scanf("%d%d", &a, &b);
        g[a].push_back(b), g[b].push_back(a);
    }		//存储树 
    dfs(1);
  //  display();
    scanf("%d", &q);
    while (q--)
    {
        scanf("%d%d", &op, &v);
        if (op == 1)
        {
            if (fa[v] && empty(fa[v])) Empty.insert(L[fa[v]]);
            Empty.erase(Empty.lower_bound(L[v]), Empty.upper_bound(R[v]));
        }
        else if (op == 2) Empty.insert(L[v]);
        else puts(empty(v) ? "0" : "1");
        //display();
    }
    return 0;
}


### Codeforces 1487D Problem Solution The problem described involves determining the maximum amount of a product that can be created from given quantities of ingredients under an idealized production process. For this specific case on Codeforces with problem number 1487D, while direct details about this exact question are not provided here, similar problems often involve resource allocation or limiting reagent type calculations. For instance, when faced with such constraints-based questions where multiple resources contribute to producing one unit of output but at different ratios, finding the bottleneck becomes crucial. In another context related to crafting items using various materials, it was determined that the formula `min(a[0],a[1],a[2]/2,a[3]/7,a[4]/4)` could represent how these limits interact[^1]. However, applying this directly without knowing specifics like what each array element represents in relation to the actual requirements for creating "philosophical stones" as mentioned would require adjustments based upon the precise conditions outlined within 1487D itself. To solve or discuss solutions effectively regarding Codeforces' challenge numbered 1487D: - Carefully read through all aspects presented by the contest organizers. - Identify which ingredient or component acts as the primary constraint towards achieving full capacity utilization. - Implement logic reflecting those relationships accurately; typically involving loops, conditionals, and possibly dynamic programming depending on complexity level required beyond simple minimum value determination across adjusted inputs. ```cpp #include <iostream> #include <vector> using namespace std; int main() { int n; cin >> n; vector<long long> a(n); for(int i=0;i<n;++i){ cin>>a[i]; } // Assuming indices correspond appropriately per problem statement's ratio requirement cout << min({a[0], a[1], a[2]/2LL, a[3]/7LL, a[4]/4LL}) << endl; } ``` --related questions-- 1. How does identifying bottlenecks help optimize algorithms solving constrained optimization problems? 2. What strategies should contestants adopt when translating mathematical formulas into code during competitive coding events? 3. Can you explain why understanding input-output relations is critical before implementing any algorithmic approach? 4. In what ways do prefix-suffix-middle frameworks enhance model training efficiency outside of just tokenization improvements? 5. Why might adjusting sample proportions specifically benefit models designed for tasks requiring both strong linguistic comprehension alongside logical reasoning skills?
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