SPFA板子

#pragma GCC optimize(3)
#include <bits/stdc++.h>
using namespace std;
const int maxn = 205;

vector<pair<int,int>>E[maxn];
int n,m;

int d[maxn],inq[maxn];
void init(){
    for(int i=0;i<maxn;i++) E[i].clear();
    for(int i=0;i<maxn;i++) inq[i] = 0;
    for(int i=0;i<maxn;i++) d[i] = 1e9;
}
int main(){

    while(cin>>n>>m){
        init();
        for(int i=0;i<m;i++){
            int x,y,z;scanf("%d%d%d",&x,&y,&z);
            E[x].push_back(make_pair(y,z));
            E[y].push_back(make_pair(x,z));
        }
        int s,t;
        scanf("%d%d",&s,&t);
        queue<int> Q;
        Q.push(s),d[s]=0,inq[s]=1;
        while(!Q.empty()){
            int now = Q.front();
            Q.pop();inq[now] = 0;
            for(int i=0;i<E[now].size();i++){
                int v = E[now][i].first;
                if(d[v]>d[now]+E[now][i].second){
                    d[v] = d[now]+E[now][i].second;
                    if(inq[v]==1) continue;
                    inq[v]=1;
                    Q.push(v);
                }
            }
        }
        if(d[t]==1e9) printf("-1\n");
        else printf(d[t]);
    }
    return 0;
}