[A* K短路 || 可持久化堆] POJ 2449 Remmarguts' Date

这就是裸的k短路了 

学习一发A*的姿势：http://yzmduncan.iteye.com/blog/1162759

这个S==T的坑要注意

#include<cstdio>#include<cstdlib>#include<algorithm>#include<cstring>#include<queue>#define V G[p].vusing namespace std;inline char nc(){static char buf[100000],*p1=buf,*p2=buf;if (p1==p2) { p2=(p1=buf)+fread(buf,1,100000,stdin); if (p1==p2) return EOF; }return *p1++;}inline void read(int &x){char c=nc(),b=1;for (;!(c>='0' && c<='9');c=nc()) if (c=='-') b=-1;for (x=0;c>='0' && c<='9';x=x*10+c-'0',c=nc()); x*=b;}const int M=200005;const int N=1005;struct edge{int u,v,w;int next;};int head[N],inum;edge G[M];inline void add(int u,int v,int w,int p){G[p].u=u; G[p].v=v; G[p].w=w; G[p].next=head[u]; head[u]=p;}int iu[M],iv[M],iw[M];int n,m,S,T,K;int dis[N],flag[N],Map[N][N];inline void Dij(int S){memset(dis,0x3f,sizeof(dis));dis[S]=0;for (int i=1;i<n;i++){int k=0;for (int j=1;j<=n;j++)if (!flag[j] && (!k || dis[j]<dis[k]))k=j;flag[k]=1;for (int j=1;j<=n;j++)if (!flag[j] && dis[j]>dis[k]+Map[k][j])dis[j]=dis[k]+Map[k][j];}}struct abcd{int u,g,f;abcd(int u=0,int g=0,int f=0):u(u),g(g),f(f) { }bool operator < (const abcd &B) const {return f>B.f;}};int cnt[N];inline int A_star(){priority_queue<abcd> Q; abcd now;if (dis[S]==0x3f3f3f3f) return -1;Q.push(abcd(S,0,dis[S]));while (!Q.empty()){now=Q.top(); Q.pop();cnt[now.u]++;if (cnt[T]==K) return now.f;if (cnt[now.u]>K) continue;for (int p=head[now.u];p;p=G[p].next)Q.push(abcd(V,now.g+G[p].w,now.g+G[p].w+dis[V]));}return -1;}int main(){int iu,iv,iw;freopen("t.in","r",stdin);freopen("t.out","w",stdout);read(n); read(m);memset(Map,0x3f,sizeof(Map));for (int i=1;i<=n;i++) Map[i][i]=0;for (int i=1;i<=m;i++)read(iu),read(iv),read(iw),add(iu,iv,iw,++inum),Map[iv][iu]=min(Map[iv][iu],iw);read(S); read(T); read(K);Dij(T);if (S==T) K++;printf("%d\n",A_star());return 0;}

UPD：可持久化堆维护 详见另一篇博文

#include<cstdio>#include<cstdlib>#include<algorithm>#include<cstring>#include<vector>#include<queue>#define cl(x) memset(x,0,sizeof(x));using namespace std;typedef long long ll;inline char nc(){  static char buf[100000],*p1=buf,*p2=buf;  if (p1==p2) { p2=(p1=buf)+fread(buf,1,100000,stdin); if (p1==p2) return EOF; }  return *p1++;}inline void read(int &x){  char c=nc(),b=1;  for (;!(c>='0' && c<='9');c=nc()) if (c=='-') b=-1;  for (x=0;c>='0' && c<='9';x=x*10+c-'0',c=nc()); x*=b;}const int M=100005;  const int N=10005;struct edge{    int u,v,next; ll w;  }G[M];  int head[N],inum=1;inline void add(int u,int v,ll w,int p){    G[p].u=u; G[p].v=v; G[p].w=w; G[p].next=head[u]; head[u]=p;  }#define V G[p].v#define U G[p].unamespace DIJ{  #define val(x) dis[H[x]]  #define K(x) (x<<1|1)>cnt?(x<<1):(val(x<<1)<val(x<<1|1)?(x<<1):(x<<1|1))    ll* dis;    int H[N];    int cnt,back[N],vst[N];    inline void Swp(int x,int y){      swap(H[x],H[y]); swap(back[H[x]],back[H[y]]);    }    inline void Up(int x){      for (;x && val(x)<val(x>>1);x>>=1) Swp(x,x>>1);              }    inline void Down(int x){      for (int tmp;(x<<1)<=cnt && val(x)>val(tmp=K(x));x=tmp) Swp(x,tmp);    }    inline void Dij(int S,int n,ll *dis){      int u; DIJ::dis=dis;      cnt=0; H[++cnt]=S; back[S]=cnt; dis[S]=0; vst[S]=1;      for (int i=1;i<=n;i++)        if (i!=S)  H[++cnt]=i,back[i]=cnt,dis[i]=1<<30,vst[i]=0;      for (int i=1;i<n;i++){        u=H[1]; vst[H[1]]=1;        Swp(1,cnt--); Down(1);        for (int p=head[u];p;p=G[p].next)  if (!vst[V] && dis[V]>dis[U]+G[p].w){    dis[V]=dis[U]+G[p].w;    Up(back[V]);  }      }    }  }inline int ran(){  static int x=31253125; x+=(x<<4)+1; return x&65536;}struct node{  node *l,*r; int p;  bool operator < (const node &B) const{    return G[p].w<G[B.p].w;  }}nodes[(N+M)*30],*root[N];int ncnt,rcnt;inline node *Me(node *A,node *B){  node *ret=nodes+(++ncnt);  if (!A || !B) { *ret=A?*A:*B; return ret; }  if (*B<*A) swap(A,B);  *ret=*A; ran()?ret->l=Me(A->l,B):ret->r=Me(A->r,B);  return ret;}int S,T;int n,m,K;int ru[M],rv[M],rw[M];ll dis[N]; int vst[N],nxt[N];int tag[M];int lst[N],pnt;inline void dfs(int u){  vst[u]=1; lst[++pnt]=u;  for (int p=head[u];p;p=G[p].next)    if (!vst[V] && dis[V]==dis[u]+G[p].w)      tag[p]=1,nxt[V]=u,dfs(V);}inline void Build(){  for (int i=1;i<=pnt;i++){    int u=lst[i];    node *last=root[nxt[u]];    for (int p=head[u];p;p=G[p].next)      if (!tag[p] && dis[V]!=1<<30){++ncnt; nodes[ncnt].p=p;last=Me(last,nodes+ncnt);      }    root[u]=last;      }}struct abcd{  ll val; node *last;  abcd(ll v,node *l) { val=v; last=l; }  bool operator < (const abcd &B) const{    return val>B.val;  }};priority_queue<abcd> Q;ll Ans=-1;  inline void Solve(){  Q.push(abcd(dis[S],NULL));  for (int i=1;i<=K && !Q.empty();i++){    abcd t=Q.top(); Q.pop();    if (i==K) { Ans=t.val; break; }    int v=t.last?G[t.last->p].v:S;    if (t.last){      if (t.last->l)Q.push(abcd(t.val-G[t.last->p].w+G[t.last->l->p].w,t.last->l));      if (t.last->r)Q.push(abcd(t.val-G[t.last->p].w+G[t.last->r->p].w,t.last->r));    }    if (root[v])      Q.push(abcd(t.val+G[root[v]->p].w,root[v]));  }}int main(){  freopen("t.in","r",stdin);  freopen("t.out","w",stdout);  read(n); read(m);  for (int i=1;i<=m;i++) read(ru[i]),read(rv[i]),read(rw[i]),add(rv[i],ru[i],rw[i],++inum);  read(S); read(T); read(K); if (S==T) K++;  DIJ::Dij(T,n,dis);  dfs(T);  cl(head); inum=1;  for (int i=1;i<=m;i++) add(ru[i],rv[i],dis[rv[i]]+rw[i]-dis[ru[i]],++inum);  Build();  Solve();  printf("%lld\n",Ans);  return 0;}