CodeForces 20C

dijkstra。唯一不同的是加入了一个记录来源的数组，最后在主函数里反向输出。

#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
== -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;
}