796D Police Stations

最新推荐文章于 2021-06-19 21:19:02 发布

原创最新推荐文章于 2021-06-19 21:19:02 发布 · 465 阅读

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本文介绍了一种基于图论的算法实现，通过多个警察节点在图中进行搜索并标记路径，以此来模拟追捕过程。文章详细展示了算法的实现过程，包括节点遍历、路径标记等关键步骤。

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#include<iostream>
#include<vector>
#include<string>
#include<set>
#include<map>
#include<algorithm>
#include<queue>
#include<stack>
#include<cstdio>
using namespace std;

int main(){
	int n, k, d;
	while (cin >> n >> k >> d){
		vector<int> police(k + 1);
		vector<bool> visit(n + 1, false);
		vector<int> remove(n);
		int result = 0;
		for (int i = 1; i <= k; i++){
			cin >> police[i];
		}
		vector<vector<pair<int, int>>> way(n + 1, vector<pair<int, int>>());
		for (int i = 1; i < n; i++){
			int u, v;
			cin >> u >> v;
			pair<int, int> temp;
			temp.second = i;
			temp.first = v;
			way[u].push_back(temp);
			temp.first = u;
			way[v].push_back(temp);
		}
		queue<pair<int, int>> q;
		for (int i = 1; i <= k; i++){
			pair<int, int> temp;
			temp.first = police[i];
			temp.second = 0;
			q.push(temp);
		}
		while (!q.empty()){
			pair<int, int> t = q.front();
			q.pop();
			int index = t.first;
			int from = t.second;
			if (visit[index]) continue;
			visit[index] = 1;
			for (int i = 0; i < way[index].size(); i++){
				pair<int, int> temp = way[index][i];
				if (temp.first != from){
					if (visit[temp.first]) remove[temp.second] = 1;
					else{
						pair<int, int> temp1;
						temp1.first = temp.first;
						temp1.second = index;
						q.push(temp1);
					}
				}
			}
		}
		for (int i = 1; i < n; i++){
			if (remove[i]) result++;
		}
		cout << result << endl;
		for (int i = 1; i < n; i++){
			if (remove[i]) cout << i << " ";
		}
		cout << endl;
	}
	return 0;
}