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
1 #include<cstdio> 2 #include<cstring> 3 #include<cstdlib> 4 5 using namespace std; 6 7 const int INF = (1<<20); 8 9 10 int dis[100000]; 11 12 struct N 13 { 14 int u,v,w; 15 struct N *next; 16 }*head[510]; 17 18 void link(int u,int v,int w) 19 { 20 N *p; 21 p = (struct N *)malloc(sizeof(struct N)); 22 p->next = NULL; 23 p->w = w; 24 p->v = v; 25 p->next = head[u]->next; 26 head[u]->next = p; 27 } 28 29 void init(int n) 30 { 31 for(int i = 1; i <= n; i++) 32 { 33 head[i] = (struct N *)malloc(sizeof(struct N)); 34 head[i]->v = -1; 35 head[i]->next = NULL; 36 } 37 } 38 39 int q[100001]; 40 int mark[510]; 41 42 bool spfa(int n) 43 { 44 for(int k = 1; k <= n; k++) 45 { 46 N *p; 47 int s = 0,e = 0,i; 48 for(i = 1; i <= n; i++) 49 mark[i] = 0; 50 mark[k] = 1; 51 q[e++] = k; 52 while(s != e) 53 { 54 int t = q[s++]; 55 56 for(p = head[t]->next; p != NULL; p = p->next) 57 { 58 if(dis[p->v] - p->w > dis[t]) 59 { 60 if(mark[p->v] < n) 61 { 62 dis[p->v] = dis[t] + p->w; 63 mark[p->v]++; 64 q[e++] = p->v; 65 } 66 else 67 return true; 68 } 69 } 70 71 72 if(s == 100001) s = 0; 73 if(e == 100001) e = 0; 74 } 75 } 76 return false; 77 } 78 79 int main() 80 { 81 int js,n,m,w,i,e,u,v,t; 82 scanf("%d",&js); 83 while(js--) 84 { 85 scanf("%d %d %d",&n,&m,&w); 86 87 init(n); 88 89 for(i = 1; i <= n; i++) 90 dis[i] = INF; 91 92 for(i = 0; i < m; i++) 93 { 94 scanf("%d %d %d",&u,&v,&t); 95 link(u,v,t); 96 link(v,u,t); 97 } 98 99 for(i = 0; i < w; i++) 100 { 101 scanf("%d %d %d",&u,&v,&t); 102 link(u,v,-t); 103 } 104 105 if(spfa(n)) 106 printf("YES\n"); 107 else printf("NO\n"); 108 109 110 } 111 return 0; 112 }
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; }