重铸华农荣光 我辈义不容辞

The eighteenth day - Bellman-ford

#include<iostream>
#include<cstring>
using namespace std;

const int N=510,M=10010;
struct Edge{
    int a,b,c;
} e[M];

int dist[N],back[N];
int n,m,k;

int Bellman_ford()
{
    memset(dist,0x3f,sizeof dist);
    dist[1]=0;

    for(int i=0;i<k;i++)
    {
        memcpy(back,dist,sizeof dist);
        for(int j=0;j<m;j++)
        {
            int a=e[j].a,b=e[j].b,c=e[j].c;
            dist[b]=min(dist[b],back[a]+c);
        }
    }

    if(dist[n]>0x3f3f3f3f/2) return 0x3f3f3f3f;
    return dist[n];
}
int main()
{
    cin>>n>>m>>k;
    for(int i=0;i<m;i++)
    {
        int a,b,c;
        cin>>a>>b>>c;
        e[i]={a,b,c};
    }

    int ans=Bellman_ford();

    if(ans==0x3f3f3f3f) puts("impossible");
    else cout<<ans;
    return 0;
}