Wormholes 虫洞 BZOJ 1715 spfa判断负环

John在他的农场中闲逛时发现了许多虫洞。虫洞可以看作一条十分奇特的有向边,并可以使你返回到过去的一个时刻(相对你进入虫洞之前)。John的每个农场有M条小路(无向边)连接着N (从1..N标号)块地,并有W个虫洞。其中1<=N<=500,1<=M<=2500,1<=W<=200。 现在John想借助这些虫洞来回到过去(出发时刻之前),请你告诉他能办到吗。 John将向你提供F(1<=F<=5)个农场的地图。没有小路会耗费你超过10000秒的时间,当然也没有虫洞回帮你回到超过10000秒以前。

NO YESSample Output


Input

* Line 1: 一个整数 F, 表示农场个数。

* Line 1 of each farm: 三个整数 N, M, W。

* Lines 2..M+1 of each farm: 三个数(S, E, T)。表示在标号为S的地与标号为E的地中间有一条用时T秒的小路。

* Lines M+2..M+W+1 of each farm: 三个数(S, E, T)。表示在标号为S的地与标号为E的地中间有一条可以使John到达T秒前的虫洞。

Output

* Lines 1..F: 如果John能在这个农场实现他的目标,输出"YES",否则输出"NO"。

Sample Input 2 3 3 1 1 2 2 1 3 4 2 3 1 3 1 3 3 2 1 1 2 3 2 3 4 3 1 8
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<string>
#include<cmath>
#include<map>
#include<set>
#include<vector>
#include<queue>
#include<bitset>
#include<ctime>
#include<deque>
#include<stack>
#include<functional>
#include<sstream>
//#include<cctype>
//#pragma GCC optimize(2)
using namespace std;
#define maxn 200005
#define inf 0x7fffffff
//#define INF 1e18
#define rdint(x) scanf("%d",&x)
#define rdllt(x) scanf("%lld",&x)
#define rdult(x) scanf("%lu",&x)
#define rdlf(x) scanf("%lf",&x)
#define rdstr(x) scanf("%s",x)
typedef long long  ll;
typedef unsigned long long ull;
typedef unsigned int U;
#define ms(x) memset((x),0,sizeof(x))
const long long int mod = 1e9;
#define Mod 1000000000
#define sq(x) (x)*(x)
#define eps 1e-5
typedef pair<int, int> pii;
#define pi acos(-1.0)
//const int N = 1005;
#define REP(i,n) for(int i=0;i<(n);i++)
typedef pair<int, int> pii;

inline int rd() {
    int x = 0;
    char c = getchar();
    bool f = false;
    while (!isdigit(c)) {
        if (c == '-') f = true;
        c = getchar();
    }
    while (isdigit(c)) {
        x = (x << 1) + (x << 3) + (c ^ 48);
        c = getchar();
    }
    return f ? -x : x;
}


ll gcd(ll a, ll b) {
    return b == 0 ? a : gcd(b, a%b);
}
int sqr(int x) { return x * x; }



/*ll ans;
ll exgcd(ll a, ll b, ll &x, ll &y) {
    if (!b) {
        x = 1; y = 0; return a;
    }
    ans = exgcd(b, a%b, x, y);
    ll t = x; x = y; y = t - a / b * y;
    return ans;
}
*/
int T;
int n, m, W;
struct node {
    int u, v, w, nxt;
}e[maxn];
int head[maxn], tot;
int dis[maxn];
void addedge(int u, int v, int w) {
    e[++tot].u = u; e[tot].v = v; e[tot].w = w;
    e[tot].nxt = head[u]; head[u] = tot;
}
int num[maxn];
bool vis[maxn];

bool spfa() {
    queue<int>q;
    q.push(1); vis[1] = 1; dis[1] = 0;
    num[1] = 1;
    while (!q.empty()) {
        int u = q.front(); q.pop();
        vis[u] = 0;
        for (int i = head[u]; i; i = e[i].nxt) {
            int v = e[i].v; int w = e[i].w;
            if (dis[v] > dis[u] + w) {
                dis[v] = dis[u] + w;
                if (!vis[v]) {
                    q.push(v); vis[v] = 1; num[v]++;
                    if (num[v] > n)return false;
                }
            }
        }
    }
    return true;
}


int main()
{
    //ios::sync_with_stdio(0);
    T = rd();
    while (T--) {
        n = rd(); m = rd(); W = rd();
        for (int i = 1; i <= n; i++)dis[i] = inf;
        ms(head); tot = 0; ms(vis); ms(e); ms(num);
        for (int i = 1; i <= m; i++) {
            int u, v, w; u = rd(); v = rd(); w = rd();
            addedge(u, v, w); addedge(v, u, w);
        }
        for (int i = 1; i <= W; i++) {
            int u, v, t;
            u = rd(); v = rd(); t = rd();
            addedge(u, v, -t);
        }
        if (spfa()) {
            cout << "NO" << endl;
        }
        else cout << "YES" << endl;
    }
    return 0;
}

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转载自www.cnblogs.com/zxyqzy/p/10351060.html