Bellman-ford算法

有边数限制的最短路

#include<bits/stdc++.h>
using namespace std;
const int N =510,M=10010,INF=0x3f3f3f3f;
struct Edge{
    int a,b,c;
}edges[M];
int n,m,k;
int dist[N],last[N];//copy数组
int bellman_ford()
{
    memset(dist,0x3f,sizeof dist);
    dist[1]=0;
    for(int i=0;i<k;i++)
    {
        memcpy(last,dist,sizeof dist);//copy过来
        for(int j=0;j<m;j++)
        {
            Edge e =edges[j];//取出边;
            dist[e.b]=min(dist[e.b],last[e.a]+e.c);
        }
    }
}
int main()
{
    cin>>n>>m>>k;
    for(int i=0;i<m;i++)
    {
        int a,b,c;
        cin>>a>>b>>c;
        edges[i]={a,b,c};
    }
    bellman_ford();
    if(dist[n]>INF/2) puts("impossible");
    else cout<<dist[n]<<endl;
    return 0;
}