图论 最短路 dijkstra

 

板子

#include<cstdio>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<queue>
#include<set>
#include<string>
using namespace std;
const int INF=0x3f3f3f3f;
typedef pair<int, int> pr;
typedef long long ll;
#define fi first
#define se second
#define me(x) memset(x, -1, sizeof(x))
#define mem(x) memset(x, 0, sizeof(x))
#define N 20000+5
#define NIL -1
struct node
{
    int next, to, w;
}edge[N];
int n, m, cnt;
int head[N], vis[N], dist[N];
struct cmp
{
    bool operator()(const int &a, const int &b) const
    {
        return dist[a]<dist[b] || (dist[a]==dist[b]&&a<b);
    }
};
void add(int u, int v, int w)
{
    edge[cnt].w=w;
    edge[cnt].to=v;
    edge[cnt].next=head[u];
    head[u]=cnt++;
}
set<int, cmp> s;
void init()
{
    cnt=0;
    s.clear();
    me(head);
    mem(vis);
    for(int i=1; i<=n; i++)
        dist[i]=INF;
}
void dijkstra()
{
    int v=1;
    s.insert(v);
    dist[v]=0;
    while(s.size())
    {
        v=*s.begin();
        s.erase(v);
        vis[v]=1;
        for(int i=head[v]; ~i; i=edge[i].next)
        {
            int t=edge[i].to;
            if(!vis[t] && dist[t]>dist[v]+edge[i].w)
            {
                s.erase(t);
                dist[t]=dist[v]+edge[i].w;
                s.insert(t);
            }
        }
    }
}
int main()
{
    int i, j, k;
    int u, v, w;
    while(cin>>n>>m)
    {
        if(!n && !m) break;
        init();
        while(m--)
            cin>>u>>v>>w, add(u, v, w), add(v, u, w);
        dijkstra();
        if(dist[n]!=INF)
            cout<<dist[n]<<endl;
        else cout<<-1<<endl;
    }
}