Dijkstra堆优化

Posted 2020-12-12 liumengliang

#include<iostream>
#include<cstdio>
#include<queue>

using namespace std;

int dis[200001],head[200001];
int n,m,a,b,c,s,cnt;
bool vis[200001];

struct edge
{
    int to;
    int dis;
    int next;
};

edge e[500001];

struct node
{
    int dis;
    int pos;
    bool operator<(const node &x)const
    {
        return x.dis<dis;
    }
};

void add_edge(int u,int v,int d)
{
    cnt++;
    e[cnt].to=v;
    e[cnt].dis=d;
    e[cnt].next=head[u];
    head[u]=cnt;
}

std::priority_queue <node> q;

void dijkstra()
{
    dis[s]=0;
    q.push((node){0,s});
    while(!q.empty())
    {
        node tmp=q.top();
        q.pop();
        int x=tmp.pos,d=tmp.dis;
        if(vis[x])
            continue;
        vis[x]=1;
        for(int i=head[x];i;i=e[i].next)
        {
            int y=e[i].to;
            if(dis[y]>dis[x]+e[i].dis)
            {
                dis[y]=dis[x]+e[i].dis;
                if(!vis[y])
                    q.push((node){dis[y],y});
            }
        }
                       }    
}

int main()
{
    scanf("%d%d%d",&n,&m,&s);
    fill(dis+1,dis+n+1,0x7fffffff);
    for(int i=1;i<=m;i++)
    {
        scanf("%d%d%d",&a,&b,&c);
        add_edge(a,b,c);
        //add_edge(b,a,c);
    }
    dijkstra();
    for(int i=1;i<=n;i++)
        printf("%d ",dis[i]);
    return 0;
}