bzoj 1598: [Usaco2008 Mar]牛跑步【A*K短路】

A*K短路模板,详见https://blog.csdn.net/z_mendez/article/details/47057461

#include<iostream>
#include<cstdio>
#include<queue>
#include<cstring>
using namespace std;
const int N=10005;
const long long inf=1e15;
int n,m,k,s,t,h[N],cnt,x[N],y[N],z[N],c[N];
long long dis[N],ans[N];
bool v[N];
struct qwe
{
    int ne,to,va;
}e[N];
struct dian
{
    int x;
    long long g,h;//g是已走过的路,h是到目的地的最短路
    dian(int X=0,long long G=0,long long H=0)
    {
        x=X,g=G,h=H;
    }
    bool operator < (const dian &a) const
    {
        return g+h>a.g+a.h;//priority是大根堆,把小于重载成大于相当于改成小根堆
    }
};
int read()
{
    int r=0,f=1;
    char p=getchar();
    while(p>'9'||p<'0')
    {
        if(p=='-')
            f=-1;
        p=getchar();
    }
    while(p>='0'&&p<='9')
    {
        r=r*10+p-48;
        p=getchar();
    }
    return r*f;
}
void add(int u,int v,int w)
{
    cnt++;
    e[cnt].ne=h[u];
    e[cnt].to=v;
    e[cnt].va=w;
    h[u]=cnt;
}
void aster()
{
    priority_queue<dian>q;
    for(int i=1;i<=k;i++)
        ans[i]=-1;
    q.push(dian(n,0,dis[n]));
    int tot=0;
    while(!q.empty())
    {
        int u=q.top().x;
        long long g=q.top().g;
        q.pop();
        c[u]++;
        if(c[u]>k)
            continue;//如果当前点第k次出队,则当前点已经不能给前k短路贡献了
        if(u==1)
            ans[++tot]=g;
        if(c[1]==k)
            return;
        for(int i=h[u];i;i=e[i].ne)
            q.push(dian(e[i].to,g+e[i].va,dis[e[i].to]));
    }
}
int main()
{
    n=read(),m=read(),k=read();
    for(int i=1;i<=m;i++)
    {
        x[i]=read(),y[i]=read(),z[i]=read();
        if(x[i]<y[i])
            swap(x[i],y[i]);
        add(y[i],x[i],z[i]);
    }
    queue<int>q;
    for(int i=1;i<=n;i++)
        dis[i]=inf;
    dis[1]=0,v[1]=1,q.push(1);
    while(!q.empty())
    {
        int u=q.front();
        q.pop();
        v[u]=0;
        for(int i=h[u];i;i=e[i].ne)
            if(dis[e[i].to]>dis[u]+e[i].va)
            {
                dis[e[i].to]=dis[u]+e[i].va;
                if(!v[e[i].to])
                    v[e[i].to]=1,q.push(e[i].to);
            }
    }
    memset(h,0,sizeof(h));
    cnt=0;
    for(int i=1;i<=m;i++)
        add(x[i],y[i],z[i]);
    aster();
    for(int i=1;i<=k;i++)
        printf("%lld\n",ans[i]);
    return 0;
}

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转载自www.cnblogs.com/lokiii/p/8996209.html