ソースコード
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <climits>
#include <cmath>
#include <complex>
#include <map>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <numeric>
#include <functional>
#include <cassert>
#include <iomanip>
using namespace std;
#define Rep(b, e, i) for(int i = b; i <= e; i++)
#define Repr(e, b, i) for(int i = e; i >= b; i--)
#define rep(n, i) Rep(0, n-1, i)
#define repr(n, i) Repr(n-1, 0, i)
#define all(v) (v).begin(), (v).end()
#define pb(v) push_back(v)
#define uniq(v) (v).erase(unique(all(v)),(v).end())
#define bitcnt(x) __builtin_popcount(x)
#define fst first
#define snd second
#define Pqaz(T) priority_queue<T,vector<T>,greater<T>>
#define Pqza(T) priority_queue<T>
#define put(x) cout << x;
#define putsp(x) cout << x << ' ';
#define putbd cout << "---------------------------------------------" << endl;
#define putln(x) cout << x << endl;
#define debug(x) cerr << #x << "=" << x << endl;
#define ENJYU std::ios::sync_with_stdio(false);std::cin.tie(0);
typedef long long ll;
typedef pair<ll, ll> llP;
typedef pair<int, int> intP;
typedef complex<double> comp;
typedef vector <int> vec;
typedef vector <ll> vecll;
typedef vector <double> vecd;
typedef vector <vec> mat;
typedef vector <vecll> matll;
typedef vector <vecd> matd;
//vector の中身を出力
template <class T>ostream &operator<<(ostream &o,const vector<T>&v)
{o<<"{";for(int i=0;i<(int)v.size();i++)o<<(i>0?", ":"")<<v[i];o<<"}";return o;}
const int MAX = 200020;
const double PI = 3.14159265358979323846;
const double EPS = 1e-12;
const int INF = 1<<29;
const ll INFL = 1e18;
const int MOD = 1000000007;
const int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
//const int dx[]={-1,-1,-1,0,1,1,1,0},dy[]={-1,0,1,1,1,0,-1,-1};
//********************************template END****************************************//
struct Dijkstra
{
//距離の型を決めよう！！！！！！！！！！！！！
typedef ll dType;
dType inf = 1e18;
typedef pair<dType, int> P;
struct edge{int to; dType cost;};
//始点からの距離
vector <dType> dis;
//隣接リスト
vector <vector <edge>> adj;
Dijkstra(int N) : dis(N, inf), adj(N){}
void add_edge(int s, int t, dType cost, bool isdirected = 0)
{
adj[s].pb((edge{t, cost}));
if (!isdirected)
{
adj[t].pb((edge{s, cost}));
}
}
void calc(int s)
{
fill(all(dis), inf);
dis[s] = 0;
priority_queue<P, vector<P>, greater<P>> q;
q.push(P(0, s));
while(!q.empty())
{
P p = q.top(); q.pop();
int now = p.snd;
if (dis[now] < p.fst)
{
continue;
}
for (edge e : adj[now])
{
if (dis[e.to] > dis[now] + e.cost)
{
dis[e.to] = dis[now] + e.cost;
q.push(P(dis[e.to], e.to));
}
}
}
}
};
void solve(void){
int N, M;
cin >> N >> M;
Dijkstra dijkstra(N);
rep(M, i)
{
int s, t, c;
cin >> s >> t >> c;
dijkstra.add_edge(s-1, t-1, c);
}
dijkstra.calc(0);
cout << (dijkstra.dis[N-1] == dijkstra.inf ? -1 : dijkstra.dis[N-1]) << endl;
}
int main(void){
solve();
//cout << "yui(*-v・)yui" << endl;
return 0;
}