[哈夫曼树 堆] BZOJ 2923 [Poi1998]The lightest language

详见BYVOID大神的blog

可以看出这是一棵哈夫曼树的若干叶子节点 

那么我们开始考虑从一棵空树扩展

如果叶节点数小于n 那么取最小的扩展

否则 如果取最小的扩展 答案更优的话继续 不优的话之后同样不会变优 

扩展时记得删去一些最大的数 保持堆的大小

#include<cstdio>#include<cstdlib>#include<algorithm>#include<queue>using 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 N=10005;struct Heap1{    priority_queue<int> Q,del;    void maintain(){ while (!Q.empty() && !del.empty() && Q.top()==del.top()) Q.pop(),del.pop(); }    int top(){ maintain(); return Q.top(); }    void pop(){ maintain(); Q.pop(); }    void push(int x){ maintain(); Q.push(x); }    void erase(int x){ maintain(); del.push(x); }    bool empty(){ maintain(); return Q.empty(); }  int size(){ maintain(); return Q.size()-del.size(); }}Max;    struct Heap2{    priority_queue<int,vector<int>,greater<int> > Q,del;    void maintain(){ while (!Q.empty() && !del.empty() && Q.top()==del.top()) Q.pop(),del.pop(); }    int top(){ maintain(); return Q.top(); }    void pop(){ maintain(); Q.pop(); }    void push(int x){ maintain(); Q.push(x); }    void erase(int x){ maintain(); del.push(x); }    bool empty(){ maintain(); return Q.empty(); }  int size(){ maintain(); return Q.size()-del.size(); }}Min;  int n,K;int a[27];int Ans=1<<30;int tot;int main(){  freopen("t.in","r",stdin);  freopen("t.out","w",stdout);  read(n); read(K);  for (int i=1;i<=K;i++) read(a[i]);  for (int i=1;i<=K;i++)    Max.push(a[i]),Min.push(a[i]),tot+=a[i];  while (1){    int x=Min.top(); Min.pop(); Max.erase(x);    tot-=x;    for (int i=1;i<=K;i++)      Min.push(x+a[i]),Max.push(x+a[i]),tot+=x+a[i];    while (Min.size()>n){      int x=Max.top(); Max.pop(); Min.erase(x);      tot-=x;    }    if (Min.size()==n){      if (Ans>tot)Ans=tot;      elsebreak;    }  }  printf("%d\n",Ans);}