bellman_ford算法

#include<iostream>
#include<cstring>
using namespace std;
const int N = 510,M = 1e4+10;
int n,m,k;
int dist[N],backup[N];
struct node{
int a,b,w;
}edge[M];
int bellman_ford(){
memset(dist,0x3f,sizeof(dist));
dist[1]=0;
for(int i=0;i<k;i++){
memcpy(backup,dist,sizeof(dist));
for(int j=0;j<m;j++){
int a=edge[j].a,b=edge[j].b,w=edge[j].w;
dist[b]=min(dist[b],backup[a]+w);
}
}
if(dist[n]>0x3f3f3f3f/2) return -1;
return dist[n];
}
int main(){
scanf("%d%d%d",&n,&m,&k);
for(int i=0;i<m;i++){
int a,b,c;
scanf("%d%d%d",&a,&b,&c);
edge[i].a=a,edge[i].b=b,edge[i].w=c;
}
int t = bellman_ford();
if(t==-1) puts("impossible");
else printf("%d",t);
return 0;
}