非传统起点终点的最短路问题

#include<bits/stdc++.h>
using namespace std;

const int N = 2510,M = 6200 * 6200 + 10;
int h[N],e[M],ne[M],w[M],idx;
int dist[N];
bool st[N];
int n,m,s,t;
queue<int> q;

void add(int a,int b,int c)
{
    e[idx] = b,ne[idx] = h[a],w[idx] = c,h[a] = idx++;
}

void spfa()
{
    memset(dist,0x3f,sizeof dist);
    dist[s] = 0;
    q.push(s);
    st[s] = true;

    while(q.size())
    {
        int p = q.front();
        q.pop();
        st[p] = false;

        for(int i = h[p];~i;i = ne[i])
        {
            int j = e[i];
            if(dist[j] > dist[p] + w[i])
            {
                dist[j] = dist[p] + w[i];
                if(!st[j])
                {
                    q.push(j);
                    st[j] = true;
                }
            }
        }
    }
}
int main()
{
    memset(h,-1,sizeof h);
    cin>>n>>m>>s>>t;
    for(int i = 0;i<m;i++)
    {
        int a,b,c;
        cin>>a>>b>>c;
        add(a,b,c),add(b,a,c);
    }
    spfa();
    cout<<dist[t]<<endl;
    return 0;
}