dijkstra

#include<iostream>
#include<cstring>
#include<algorithm>
#include<queue>
using namespace std;
typedef pair<int,int>PII;
const int N=2600,M=6200*2;
int T,C,S,E;

int h[N],e[M],ne[M],w[M],idx;
int dist[N];
bool st[N];


void add(int a,int b,int c)
{
    e[idx]=b,w[idx]=c,ne[idx]=h[a],h[a]=idx++;
}
int dijkstra()
{
   memset(dist,0x3f,sizeof dist);
   dist[S]=0;
  priority_queue<PII,vector<PII>,greater<PII>>q;

   q.push({0,S});
   while(q.size())
   {
       auto t=q.top();
       q.pop();
       int ver=t.second,distance=t.first;
       if(st[ver])continue;
       st[ver]=true;
       for(int i=h[ver];~i;i=ne[i])
       {
           int j=e[i];
           if(dist[j]>distance+w[i])
           {
               dist[j]=distance+w[i];
               q.push({dist[j],j});
           }


       }


   }    
    return dist[E];
}

int main()
{
    cin>>T>>C>>S>>E;
    memset(h,-1,sizeof h);
    while(C--)
    {
        int a,b,c;
        scanf("%d%d%d",&a,&b,&c);
        add(a,b,c),add(b,a,c);
    }

    cout<<dijkstra()<<endl;
    return 0;
}

spfa

#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
int t,c,s,de;
const int N=2510,M=6300*2;
int h[N],e[M],ne[M],w[M],idx;
int dist[N],q[N];
bool st[N];

void add(int a,int b,int c)
{
    e[idx]=b,w[idx]=c,ne[idx]=h[a],h[a]=idx++;
}
void spfa()
{
    memset(dist,0x3f,sizeof dist);
    dist[s]=0;
    int hh=0,tt=1;
    q[0]=s;st[s]=true;
    while(hh!=tt)//优先队列判断不相等为空  
    {
        int t=q[hh++];
        if(hh==N)hh=0;
        st[t]=false;
        for(int i=h[t];~i;i=ne[i])//t所接的边
        {
            int j=e[i];
            if(dist[j]>dist[t]+w[i])
            {
                dist[j]=dist[t]+w[i];
                if(!st[j]){
                    q[tt++]=j;
                    if(tt==N)tt=0;
                    st[j]=true;
                }
            }
        }
    }
}
int main()
{
    cin>>t>>c>>s>>de;
    memset(h,-1,sizeof h);
    while(c--)
    {
        int a,b,c;
        scanf("%d%d%d",&a,&b,&c);
        add(a,b,c),add(b,a,c);
    }
    spfa();
    cout<<dist[de]<<endl;
    return 0;
}