ZOJ1117 POJ1521 HDU1053 Entropy，哈夫曼编码问题

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经典的哈夫曼编码问题，贪心算法。
/******************************************************************************* # Author : Neo Fung # Email : neosfung@gmail.com # Last modified: 2011-12-29 19:36 # Filename: ZOJ1117 POJ1521 HDU1053 Entropy.cpp # Description :  ******************************************************************************/// #include "stdafx.h"// #define DEBUG#include <fstream>#include <stdio.h>#include <iostream>#include <string.h>#include <string>#include <memory.h>#include <limits.h>#include <algorithm>#include <math.h>#include <numeric>#include <functional>#include <ctype.h>#define MAX 128using namespace std;struct NODE{  int weight,index;  NODE *lhs,*rhs;}node[MAX*MAX];int n_count;int num[MAX];bool inline cmp(const NODE &lhs,const NODE &rhs){  return lhs.weight>rhs.weight;}void func(NODE *p_arry,const int &len){  if(len<2)    return;  sort(p_arry,p_arry+len,cmp);  swap(p_arry[len-2],p_arry[n_count]);  p_arry[len-2].lhs=&p_arry[len-1];  p_arry[len-2].rhs=&p_arry[n_count];  p_arry[len-2].weight=p_arry[len-1].weight+p_arry[n_count].weight;  ++n_count;}int sum_len(const NODE *p,const int &len){  if(p->lhs==NULL)    return p->weight*len;  else  {    return sum_len(p->lhs,len+1) + sum_len(p->rhs,len+1);  }}int main(void){#ifdef DEBUG    freopen("C:/Users/neo/Desktop/stdin.txt","r",stdin);  freopen("C:/Users/neo/Desktop/stdout.txt","w",stdout); #endif    char str[MAX*MAX];  while(scanf("%s",str))  {    if(!strcmp(str,"END"))      break;    memset(num,0,sizeof(num));    for(int i=0;i<strlen(str);++i)      ++num[str[i]];    sort(num,num+MAX,greater<int>());    int len=0;    for(;num[len];++len)    {      node[len].lhs=NULL;      node[len].rhs=NULL;      node[len].weight=num[len];      node[len].index=len;    }    if(len>1)    {      n_count=len;      for(int i=len;i>1;--i)        func(node,i);      int ans=sum_len(&node[0],0);      printf("%d %d %.1lf\n",strlen(str)*8,ans,double(strlen(str)*8)/double(ans));    }    else      printf("%d %d %.1lf\n",strlen(str)*8,num[0],double(strlen(str)*8)/double(num[0]));  }  return 0;}