poj 3259 负环

题意：判是否有负环

分析：SPFA 入队n次以上有负环

 

 

#define M 505
struct Node{
    int v,val,next;
}edge[M<<4];
int len;

int head[M],  n,  rt;
int dist[M], pre[M], vis[M], times[M];

void add(int &kind, int v, int val){//起点  终点  权值
    edge[len].next = kind;
    edge[len].v = v;
    edge[len].val = val;
    kind = len++;
}

deque<int> que;

bool SPFA(){
    que.push_back(rt);  dist[rt]=0;  //pre[rt]=-1;
    while( !que.empty() ){
        int u = que.front(); que.pop_front(); vis[u] = 0;
        for(int i = head[u]; i != -1; i = edge[i].next) {
            int v = edge[i].v,  val = edge[i].val;
            if(dist[v] > dist[u]+val) {
                dist[v] = dist[u]+val; //pre[v]=u;
                if( !vis[v] ){
                    int t = que.front();
                    if(dist[v] > dist[t]) que.push_back(v);
                    else que.push_front(v);
                    vis[v] = 1; times[v]++;
                    if(times[v]>=n) return false;//入队次数>=n  则有负环
                }
            }
        }
    }
    return true;
}

void init(){
    len = 0;
    memset(head,-1, sizeof head);
    memset(dist, 1, sizeof dist);
    memset(times, 0, sizeof times);
    memset( vis, 0, sizeof vis );
    //memset( pre, 1, sizeof pre );
    while(!que.empty()) que.pop_front();
}

void build(){       // 处理rt
    int m,w, a, b, c;           rt=1;
    scanf("%d%d%d", &n, &m, &w);
    while( m-- ){
        scanf("%d%d%d", &a, &b, &c);
        add(head[a], b, c);
        add(head[b], a, c);
    }
    while( w-- ){
        scanf("%d%d%d", &a, &b, &c);
        add(head[a], b, -c);
    }
}

int main(){                //  READ
    int f;
    scanf("%d",&f);
    while(f--){
        init();
        build();
        if(SPFA()) printf("NO\n");
        else printf("YES\n");
    }
    return 0;
}