传送门:https://www.luogu.org/problemnew/show/P1339
dijkstra模板题,不多说了
#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5+7;
const int INF = 1e9+7;
struct edge
{
int to;
int cost;
};
struct node
{
int now;
int cost;
bool operator<(const node& a)const
{
return cost>a.cost;
}
};
vector<edge> G[maxn];
int d[maxn];
void init()
{
fill(d,d+maxn,INF);
}
void dijkstra(int s)
{
priority_queue<node> q;
d[s] = 0;
q.push((node){s,d[s]});
while(!q.empty())
{
node tmp = q.top();
q.pop();
if(d[tmp.now]<tmp.cost) continue;
for(int i=0;i<G[tmp.now].size();i++)
{
int v = G[tmp.now][i].to;
if(d[v]>d[tmp.now]+G[tmp.now][i].cost)
{
d[v] = d[tmp.now] + G[tmp.now][i].cost;
q.push((node){v,d[v]});
}
}
}
}
int main()
{
int t,c,ts,te;
cin>>t>>c>>ts>>te;
init();
for(int i=1;i<=c;i++)
{
int rs,re,ci;
cin>>rs>>re>>ci;
G[rs].push_back((edge){re,ci});
G[re].push_back((edge){rs,ci});
}
dijkstra(ts);
cout<<d[te]<<endl;
return 0;
}