邻接表法

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
const int N = 510, M = 100010;
int h[N],e[M],ne[M],w[M],idx;
int dist[N];
bool st[N];
int n,m;
void add(int a,int b,int c)
{
    e[idx]=b,ne[idx]=h[a],w[idx]=c,h[a]=idx++;
}
int dijkstra()
{
    memset(dist,0x3f,sizeof dist);
    dist[1]=0;
    for (int i=1;i<=n;i++)
    {
        int t=-1;
        for (int j=1;j<=n;j++)
        {
            if (!st[j]&&(t==-1||dist[t]>dist[j]))
                t=j;
        }
        st[t]=true;
        for (int i=h[t];i!=-1;i=ne[i])
        {
            int j=e[i];
            dist[j]=min(dist[j],dist[t]+w[i]);
        }
    }
    if (dist[n]==0x3f3f3f3f) return -1;
    return dist[n];
}
int main()
{
    memset(h,-1,sizeof h);
    scanf("%d%d",&n,&m);
    while (m--)
    {
        int a,b,c;
        scanf("%d%d%d",&a,&b,&c);
        add(a,b,c);
    }
    int ans=dijkstra();
    printf("%d\n",ans);
    return 0;
}

邻接矩阵版本

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 510;
int dist[N];
int g[N][N];
bool st[N];
int n,m;
int dijkstra()
{
    memset(dist,0x3f,sizeof dist);
    dist[1]=0;
    for (int i=0;i<n;i++)
    {
        int t=-1;
        for (int j=1;j<=n;j++)
        {
            if (!st[j]&&(t==-1||dist[t]>dist[j]))
                t=j;
        }
        st[t]=true;
        for (int j=1;j<=n;j++)
            dist[j]=min(dist[j],dist[t]+g[t][j]);
    }
    if (dist[n]==0x3f3f3f3f) return -1;
    return dist[n];
}
int main()
{
    scanf("%d%d",&n,&m);
    memset(g,0x3f,sizeof g);
    while (m--)
    {
        int a,b,c;
        scanf("%d%d%d",&a,&b,&c);
        g[a][b]=min(g[a][b],c);
    }

    int ans=dijkstra();
    printf("%d\n",ans);
    return 0;
}