1 #include<iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<queue> 5 using namespace std; 6 struct edge{ 7 int to; 8 int next; 9 int len; 10 }qwq[100005]; 11 queue<int>pq; 12 int edge_cnt=0,n,m,head[100005],in[100005],stk[100005],dist[100005]; 13 bool spfa() 14 { 15 memset(in,0,sizeof(in)); 16 memset(stk,0,sizeof(stk)); 17 memset(dist,-1,sizeof(dist)); 18 dist[0]=0; 19 while(!pq.empty()) 20 { 21 pq.pop(); 22 } 23 pq.push(0); 24 in[0]++; 25 stk[0]=1; 26 while(!pq.empty()) 27 { 28 int qaq=pq.front();pq.pop(); 29 stk[qaq]=0; 30 for(int i = head[qaq];i!=-1;i=qwq[i].next) 31 { 32 int v=qwq[i].to; 33 if(dist[v]<dist[qaq]+qwq[i].len) 34 { 35 dist[v]=dist[qaq]+qwq[i].len; 36 if(!stk[v]) 37 { 38 pq.push(v); 39 in[v]++; 40 stk[v]=1; 41 if(in[v]>n+1){ 42 return false; 43 } 44 } 45 } 46 } 47 } 48 return true; 49 } 50 void add(int x,int y,int z) 51 { 52 qwq[edge_cnt].to=y; 53 qwq[edge_cnt].next=head[x]; 54 qwq[edge_cnt].len=z; 55 head[x]=edge_cnt++; 56 } 57 int main() 58 { 59 scanf("%d%d",&n,&m); 60 memset(head,-1,sizeof(head)); 61 edge_cnt=0; 62 for(int i = 0 ; i < m ;i++) 63 { 64 int a,b,c; 65 scanf("%d%d%d",&a,&b,&c); 66 add(a,b,c); 67 } 68 if(!spfa())printf("-1 "); 69 return 0; 70 }