堆优化dij

Posted 2021-02-10 esquecer

#include<iostream>
#include<cstdio>
#include<queue>
using namespace std;
int n,m,S,tot,Next[500010],head[20000],tree[500010],val[500010];
bool visit[20000];
long long dis[20000];
struct cmp
{
    bool operator()(int a,int b)
    {
        return dis[a]>dis[b];
    }
};
priority_queue<int,vector<int>,cmp> Q;
void add(int x,int y,int z)
{
    tot++;
    Next[tot]=head[x];
    head[x]=tot;
    tree[tot]=y;
    val[tot]=z;
}
int main()
{
    scanf("%d%d%d",&n,&m,&S);
    tot=0;
    for (int i=1;i<=m;i++)
    {
        int x,y,z;
        scanf("%d%d%d",&x,&y,&z);
        if (x==y) continue;
        add(x,y,z);
    }
    for (int i=1;i<=n;i++) 
    {
        visit[i]=false;
        dis[i]=2147483647;
    }
    Q.push(S);
    dis[S]=0;
    while (!Q.empty())
    {
        int u=Q.top();
        Q.pop();
        if (visit[u]) continue;
        visit[u]=true;
        for (int i=head[u];i;i=Next[i])
        {
            int v=tree[i];
            if (!visit[v]&&dis[v]>dis[u]+(long long)val[i])
            {   
                dis[v]=dis[u]+val[i];
                Q.push(v);
            }
        }
    }
    for (int i=1;i<=n-1;i++) printf("%lld ",dis[i]);
    printf("%lld
",dis[n]);
    return 0;
}