POJ 3259 Wormholes(水题)

版权声明：听说这里让写版权声明～～～ https://blog.csdn.net/m0_37691414/article/details/82083245

解析：判断是否存在回路。

#include<iostream>
#include<vector>
#include<map>
#include<cstdio>
#include<cstring>
#include<queue>
using namespace std;
const int INF = 0x3f3f3f3f;
const int maxn = 5210;
int dis[maxn], cnt[maxn];
bool visit[maxn];
vector<pair<int, int> > e[maxn];
int n, m, W;
bool solve(){
	memset(visit, false, sizeof(visit));
	memset(cnt, 0, sizeof(cnt));
	queue<int> q;
	q.push(1);
	visit[1] = true;
	dis[1] = 0;
	cnt[1]++;
	while(!q.empty()){
		int from = q.front();
		q.pop();
		visit[from] = false;
		for(int i = 0; i < e[from].size(); ++i){
			int to = e[from][i].first;
			int w = e[from][i].second;
			if(dis[to] > dis[from] + w){
				dis[to] = dis[from] + w;
				if(visit[to] == false)
					visit[to] = true, q.push(to), cnt[to]++;
				if(cnt[to] > n)	return true;
			}
		}
	}
	return false;
}
int main(){
	int T, from, to, w;
	scanf("%d", &T);
	while(T--){
		fill(dis, dis + maxn, INF);
		scanf("%d%d%d", &n, &m, &W);
		for(int i = 0; i <= n; ++i)
			e[i].clear();
		for(int i = 1; i <= m; ++i){
			scanf("%d%d%d", &from, &to, &w);
			e[from].push_back(make_pair(to, w));
			e[to].push_back(make_pair(from, w));
		}
		for(int i = 1; i <= W; ++i){
			scanf("%d%d%d", &from, &to, &w);
			e[from].push_back(make_pair(to, -w));
		}
		if(solve())	printf("YES\n");
		else printf("NO\n");
	}
	return 0;
}