【Codeforces 20C】 Dijkstra？

【题目链接】

           点击打开链接

【算法】

          dijkstra

【代码】

         

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e15;
const ll MAXN = 1e5;

ll n,m,u,v,w,i,p,to,cost,x;
ll dist[MAXN+10],vis[MAXN+10],last[MAXN+10];
priority_queue< pair<ll,ll> > q;
vector< pair<ll,ll> > E[MAXN+10];
vector<ll> path;

template <typename T> inline void read(T &x) {
        ll f = 1; x = 0;
        char c = getchar();
        for (; !isdigit(c); c = getchar()) { if (c == '-') f = -f; }
        for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + c - '0';
        x *= f;
}
template <typename T> inline void write(T x) {
        if (x < 0) { x = -x; putchar('-'); }
        if (x > 9) write(x/10);
        putchar(x%10+'0');    
}
template <typename T> inline void writeln(T x) {
        write(x);
        puts("");    
}

int main() {
    
    read(n); read(m);
    for (i = 1; i <= m; i++) {
            read(u); read(v); read(w);
            E[u].push_back(make_pair(v,w));
            E[v].push_back(make_pair(u,w));
    }
    for (i = 2; i <= n; i++) dist[i] = INF;
    q.push(make_pair(0,1));
    while (!q.empty()) {
            x = q.top().second; q.pop();
            if (vis[x]) continue;    
            vis[x] = 1;
            for (i = 0; i < E[x].size(); i++) {
                    to = E[x][i].first;
                    cost = E[x][i].second;
                    if (dist[x] + cost < dist[to]) {
                            dist[to] = dist[x] + cost;
                            q.push(make_pair(-dist[to],to));
                            last[to] = x;
                    }
            }
    }
    
    if (dist[n] == INF) {
            puts("-1");
            return 0;
    }
    
    p = n;
    while (p) {
            path.push_back(p);
            p = last[p];
    }
    
    reverse(path.begin(),path.end());
    
    for (i = 0; i < path.size(); i++) {
            write(path[i]);
            if (i < path.size() - 1) putchar(' ');    
    }
    
    return 0;
}