Remmarguts' Date-A-STAR

• Remmarguts' Date

•  POJ - 2449 
• 题意：就是求第k短路但是有起点终点相等的情况

• #include<algorithm>
  #include<iostream>
  #include<cstdlib>
  #include<cstring>
  #include<cstdio>
  #include<cmath>
  #include<queue>
  #define LL long long
  #define inf 2147483640
  using namespace std;
  
  const int maxn=100010;
  struct edge
  {
      int to,next,w;
  } e[maxn<<1];
  int head[maxn],cnts[maxn],dis[maxn],vis[maxn];
  int n,m,S,T,K,cnt,U[maxn],V[maxn],W[maxn];
  struct data
  {
      int num,w;
      friend bool operator < (const data a,const data b)
      {
          return a.w>b.w;
      }
  };
  struct node
  {
      int num,g,h;
      friend bool operator < (const node a,const node b)
      {
          return a.g+a.h>b.g+b.h;//返回函数f小的
      }
  };
  void link(int u,int v,int w)
  {
      e[++cnt]=(edge)
      {
          v,head[u],w
      };
      head[u]=cnt;
  }
  void Dijkstra()
  {
      for (int i=1; i<=n; i++) dis[i]=inf;
      dis[T]=0;
      priority_queue<data> q;
      data x=(data)
      {
          T,0
      };
      q.push(x);
      while (!q.empty())
      {
          x=q.top();
          q.pop();
          if (vis[x.num]) continue;
          vis[x.num]=1;
          for (int i=head[x.num]; i; i=e[i].next) if (dis[e[i].to]>x.w+e[i].w)
              {
                  dis[e[i].to]=e[i].w+x.w;
                  q.push((data)
                  {
                      e[i].to,dis[e[i].to]
                  });
              }
      }
  }
  int Astar()
  {
      node x=(node)
      {
          S,0,dis[S]
      };
      priority_queue<node> q;
      q.push(x);
      while (!q.empty())
      {
          x=q.top();
          q.pop();
          cnts[x.num]++;
          if (cnts[x.num]>K) continue;
          if (cnts[T]==K) return x.g;
          for (int i=head[x.num]; i; i=e[i].next) q.push((node)
          {
              e[i].to,x.g+e[i].w,dis[e[i].to]
          });
      }
      return -1;
  }
  int main()
  {
      scanf("%d%d",&n,&m);
      for (int i=1; i<=m; i++)
      {
          scanf("%d%d%d",&U[i],&V[i],&W[i]);
          link(V[i],U[i],W[i]);
      }
      scanf("%d%d%d",&S,&T,&K);
      if (S==T) K++;
      Dijkstra();
      memset(head,0,sizeof(head));
      cnt=0;
      for (int i=1; i<=m; i++) link(U[i],V[i],W[i]);
      int ans=Astar();
      printf("%d",ans);
      return 0;
  }
  

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