Codeforces 20C

codeforces20C.cpp

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <queue>
#include <cmath>
#define abs(x) ((x)>0?(x):(0-(x)))
#define MAX(a,b) (a>b?a:b)
#include <set>
#include <climits>
#define LL long long
using namespace std;

const int maxn = 400005;
const LL maxd = 1E13;
int v[maxn],w[maxn],next[maxn],pre[maxn],res[maxn];
int first[maxn],inq[maxn],e;
LL d[maxn];

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


void addeage(int x,int y,int z)
{
    v[e]=y;
    w[e]=z;
    next[e]=first[x];
    first[x]=e;
    e++;
}

void spfa(int s)
{
    queue<int> q;
    for(int i =0;i<maxn;i++)
        d[i]=maxd;
    d[s]=0;inq[s]=1;q.push(s);
    while(q.empty()==false)
    {
        int u = q.front();
        q.pop();
        inq[u]=0;
        for(int i =first[u];i!=-1;i=next[i])
        {
            if(d[v[i]]>d[u]+w[i])
            {
                d[v[i]]=(d[u]+w[i]);
                pre[v[i]]=u;
                if(inq[v[i]]==0)
                {
                    q.push(v[i]);
                    inq[v[i]]=1;
                }
            }
        }
    }
}

int main()
{
    init();
    int m,n;
    scanf("%d%d",&m,&n);
    int x,y,z;
    while(n--)
    {
        scanf("%d%d%d",&x,&y,&z);
        addeage(x,y,z);
        addeage(y,x,z);
    }
    spfa(1);
    if(d[m]==maxd)
        printf("-1");
    else
    {
        int now=m;
        int cnt=0;
        while(now!=1)
        {
           res[cnt++] = now;
           now = pre[now];
        }
        res[cnt++] = 1;
        for(int i = cnt-1;i >= 0;i--)
            printf("%d ",res[i]);
    }
    return 0;
}