词频统计程序

1. 基本要求
   可导入任意英文文本文件，统计该英文文本中单词的总数，出现的次数及频率。将统计结果导出到指定文本中。
2. 源代码

#include <cstdio>
#include <string>
#include <vector>
#include <algorithm>
#include <cstdlib>
#include <ctime>


using namespace std;
#define MAX_LENGTH 1<<10//单词的最大长度


typedef struct{
   string str;
   int cnt;
}word;


int number_of_words=0;//单词统计总数
vector<string> virtual_word;
vector<string> raw_word;
vector<word> word_statistics;//统计结果集



bool cmp_raw_word(const string &a,const string &b){return a<b;}



bool cmp_word_statistics(const word &a,const word &b){return a.cnt>b.cnt;}



bool skip(){ scanf("%*[^a-z||A-Z]"); return true;}


int main()
{
   /*初始化时间*/
   clock_t start,finish;
   double totaltime;
   start=clock();


   printf("Wait for a moment please.\n");


   /*定义缓存空间*/
   word w;
   char _word[MAX_LENGTH];


   vector<string>::iterator it,last;
   vector<word>::iterator wit;


  
   freopen("virtual.ini","r",stdin);
   while(skip()&&scanf("%[a-zA-Z]",_word)!=EOF) virtual_word.push_back(_word);


   
   sort(virtual_word.begin(),virtual_word.end(),cmp_raw_word);


   /*读取 in.txt 文件中所有英文单词*/
   freopen("in.txt","r",stdin);
   while(skip()&&scanf("%[a-zA-Z]",_word)!=EOF)
   {
      number_of_words++;
      /*将只有首字母大写的单词的首字母转换成小写*/
      if(_word[1]!='\0'&&isupper(_word[0])&&islower(_word[1])) _word[0]|=1<<5;
      raw_word.push_back(_word);
   }


   /*统计信息输入至 out.txt 文件并输出相关说明信息*/
   freopen("out.txt","w",stdout);
   printf("-----------------------------------------------\n");
   printf("%d words be counted! \nDetails are as follow:\n",number_of_words);
   printf("no.   word              time          frequency\n");
   printf("-----------------------------------------------\n");


   /*若没有检测到输入时,结束程序并返回提示信息*/
   if(!raw_word.size())
   {
      printf("There is no word in the \"in.txt\" or \"in.txt\" inexistence!\n");
      printf("-----------------------------------------------\n");
      return 0;
   }


   /*对单词集进行字典排序以便进行出现次数统计操作*/
   sort(raw_word.begin(),raw_word.end(),cmp_raw_word);
   for(last=raw_word.begin(),it=raw_word.begin()+1;it!=raw_word.end();it++)
   {
      if(*it!=*last)
      {
         w.str=*last;
         w.cnt=it-last;
         /*得到的统计结果在 virtual_word 集合中验证,未在 virtual_word 集合中出现才计入结果*/
         if(!binary_search(virtual_word.begin(),virtual_word.end(),*last)) word_statistics.push_back(w);
         last=it;
      }
   }


   
   w.str=*last;
   w.cnt=it-last;
   if(!binary_search(virtual_word.begin(),virtual_word.end(),*last)) word_statistics.push_back(w);


   /*对结果集进行出现次数关键词降序排序*/
   sort(word_statistics.begin(),word_statistics.end(),cmp_word_statistics);
   bool b=false;
   for(wit=word_statistics.begin();wit!=word_statistics.end();wit++)
   {
      
      if((*wit).cnt*1.0/number_of_words>=0.05||((*wit).cnt>=2&&(*wit).cnt*100.0/number_of_words>=0.01)){
          printf("%-5d %-16s %5d %17.3lf%%\n",wit-word_statistics.begin()+1,((*wit).str).c_str(),(*wit).cnt,(*wit).cnt*100.0/number_of_words);
          b=true;
      }
   }


   
   if(!b)printf("no appropriate word!\n");
   printf("-----------------------------------------------\n");


   /*计算并输出统计程序消耗的时间*/
   finish=clock();
   totaltime=(double)(finish-start)/CLOCKS_PER_SEC;
   printf("The program cost %.4lf second(s)",totaltime);
   return 0;
}