list1307.cpp

teach yourself C++ in 21 days 第五版

#include <iostream>
#include <ctype.h>
#include <string.h>

bool GetWord(char* theString, 
          char* word, int& wordOffset);

// driver program
int main()
{
   const int bufferSize = 255;
   char buffer[bufferSize+1];   // hold the entire string
   char word[bufferSize+1];     // hold the word
   int wordOffset = 0;          // start at the beginning

   std::cout << "Enter a string: ";
   std::cin.getline(buffer,bufferSize);

   while (GetWord(buffer,word,wordOffset))
   {
      std::cout << "Got this word: " << word << std::endl;
   }
   return 0;
}

// function to parse words from a string.
bool GetWord(char* theString, char* word, int& wordOffset)
{
   if (!theString[wordOffset])  // end of string?
       return false;

   char *p1, *p2;
   p1 = p2 = theString+wordOffset;  // point to the next word

   // eat leading spaces
   for (int i = 0; i<(int)strlen(p1) && !isalnum(p1[0]); i++)
      p1++;

   // see if you have a word
   if (!isalnum(p1[0]))
      return false;

   // p1 now points to start of next word
   // point p2 there as well
   p2 = p1;

   // march p2 to end of word
   while (isalnum(p2[0]))
      p2++;

   // p2 is now at end of word
   // p1 is at beginning of word
   // length of word is the difference
   int len = int (p2 - p1);

   // copy the word into the buffer
   strncpy (word,p1,len);

   // null terminate it
   word[len]='\0';

   // now find the beginning of the next word
   for (int j = int(p2-theString); j<(int)strlen(theString)
      && !isalnum(p2[0]); j++)
   {
      p2++;
   }

   wordOffset = int(p2-theString);

   return true;
}