CodeForces 20C

dijkstra。唯一不同的是加入了一個記錄來源的數組，最後在主函數裏反向輸出。

#include <iostream>
#include <queue>
#include <memory.h>
#include <fstream>
using namespace std;

int n,m;
int v[200002],w[200002],next[200002];
int first[100003],e;
int pre[100002],res[100002];
long long d[100002];
typedef pair<long long,int> pii;

void init()
{
    e = 0;
    memset(first,-1,sizeof(first));
}

void add_edge(int a,int b,int c)
{
    v[e] = b;w[e] = c;
    next[e] = first[a];first[a] = e ++;
}

void dijkstra(int src){
    priority_queue <pii,vector<pii>,greater<pii> > q;
    memset(d,-1,sizeof(d));
    d[src] = 0;
    q.push(make_pair(0,src));
    while(!q.empty()){
        while(!q.empty() && q.top().first > d[q.top().second])    q.pop();
        if(q.empty())   break;
        int u = q.top().second;
        q.pop();
        for(int i = first[u];i != -1;i = next[i]){
            if(d[v[i]] == -1 || d[v[i]] > d[u]+w[i]){
                d[v[i]] = d[u]+w[i];
                q.push(make_pair(d[v[i]],v[i]));
                pre[v[i]] = u;
            }
        }
    }
}

int main()
{
    //ifstream cin("in.txt");
    cin >> n >> m;
    init();
    int a,b,c;
    for(int i = 0;i < m;i ++)
    {
        cin >> a >> b >> c;
        add_edge(a,b,c);
        add_edge(b,a,c);
    }
    dijkstra(1);
    int now = n,cnt = 0;
    if(d[n] == -1)  {cout << -1;return 0;}
    while(now != 1)
    {
        res[cnt ++] = now;
        now = pre[now];
    }
    res[cnt] = 1;
    for(int i = cnt;i >= 0;i --)  cout << res[i] << ' ';
    return 0;
}