POJ 3259 Wormholes

这个题意 就是利用虫洞时光倒流，题目中给出的虫洞史有向边！

SPFA水过~~这个跑了204ms  第一次写  应该是邻接矩阵的缘故……sad

#include<cstdio>
#include<cstring>
#include<cstdlib>

using namespace std;

const int INF = (1<<20);


int dis[100000];

struct N
{
    int u,v,w;
    struct N *next;
}*head[510];

void link(int u,int v,int w)
{
    N *p;
    p = (struct N *)malloc(sizeof(struct N));
    p->next = NULL;
    p->w = w;
    p->v = v;
    p->next = head[u]->next;
    head[u]->next = p;
}

void init(int n)
{
    for(int i = 1; i <= n; i++)
    {
        head[i] = (struct N *)malloc(sizeof(struct N));
        head[i]->v = -1;
        head[i]->next = NULL;
    }
}

int q[100001];
int mark[510];

bool spfa(int n)
{
    for(int k = 1; k <= n; k++)
    {
        N *p;
        int s = 0,e = 0,i;
        for(i = 1; i <= n; i++)
            mark[i] = 0;
        mark[k] = 1;
        q[e++] = k;
        while(s != e)
        {
            int t = q[s++];

            for(p = head[t]->next; p != NULL; p = p->next)
            {
                if(dis[p->v] - p->w > dis[t])
                {
                    if(mark[p->v] < n)
                    {
                        dis[p->v] = dis[t] + p->w;
                        mark[p->v]++;
                        q[e++] = p->v;
                    }
                    else
                        return true;
                }
            }


            if(s == 100001) s = 0;
            if(e == 100001) e = 0;
        }
    }
    return false;
}

int main()
{
    int js,n,m,w,i,e,u,v,t;
    scanf("%d",&js);
    while(js--)
    {
        scanf("%d %d %d",&n,&m,&w);

        init(n);

        for(i = 1; i <= n; i++)
            dis[i] = INF;

        for(i = 0; i < m; i++)
        {
            scanf("%d %d %d",&u,&v,&t);
            link(u,v,t);
            link(v,u,t);
        }

        for(i = 0; i < w; i++)
        {
            scanf("%d %d %d",&u,&v,&t);
            link(u,v,-t);
        }

        if(spfa(n))
            printf("YES\n");
        else printf("NO\n");


    }
    return 0;
}

这个是bellman ford  跑了63ms……

#include<cstdio>
#include<cstring>
#include<cstdlib>

using namespace std;

const int INF = (1<<20);

struct N
{
    int s,e,t;
}edge[100000];

int dis[100000];

bool bell_man(int n,int e)
{
    bool flag;
    for(int i = 0;i < n-1; i++)
    {
        flag = false;
        for(int j = 0;j < e; j++)
            if(dis[edge[j].e] > dis[edge[j].s] + edge[j].t)
            {
                dis[edge[j].e] = dis[edge[j].s] + edge[j].t;
                flag = true;
            }
        if(!flag)
            break;
    }
    for(int k = 0;k < e; k++)
        if(dis[edge[k].e] > dis[edge[k].s] + edge[k].t)
            return true;
    return false;
}

int main()
{
    int js,n,m,w,i,e,u,v,t;
    scanf("%d",&js);
    while(js--)
    {
        scanf("%d %d %d",&n,&m,&w);
        
        for(i = 1;i <= n; i++)
            dis[i] = INF;
        
        for(e = 0,i = 0;i < m; i++)
        {
            scanf("%d %d %d",&u,&v,&t);
            edge[e].s = edge[e+1].e = u;
            edge[e].e = edge[e+1].s = v;
            edge[e].t = edge[e+1].t = t;
            e += 2;
        }
        
        for(i = 0;i < w; i++)
        {
            scanf("%d %d %d",&u,&v,&t);
            edge[e].s = u;
            edge[e].e = v;
            edge[e].t = -t;
            e++;
        }
        
        if(bell_man(n,e))
            printf("YES\n");
        else printf("NO\n");
    
    }
    return 0;
}