Bellman-Ford(有边数限制的最短路)

#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
const int N=510,M=10010;
int n,m,k;
int dist[N],backup[N];
struct Edge
{
int a,b,w;
}edges[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=edges[j].a,b=edges[j].b,w=edges[j].w;
dist[b]=min(dist[b],backup[a]+w);
}
}
if(dist[n]>0x3f3f3f3f/2) return -1;
return dist[n];
}
int main()
{
cin>>n>>m>>k;
for(int i=0;i<m;i++)
{
int a,b,w;
cin>>a>>b>>w;
edges[i]={a,b,w};
}
int t=bellman_ford();
if(t==-1) puts("impossible");
else cout<<t<<endl;
return 0;
}