wordlist.cpp

为SSD5课程《数据结构与算法》中的练习

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>

using namespace std;

const int INITIAL_LIST_CAPACITY = 10;

void build_wordlist (string* &word_list, int &capacity, string filename) {

  ifstream words;
  string word;
  int size = 0;

  // Allocate the space for the word list
  word_list = new string[INITIAL_LIST_CAPACITY];
  capacity = INITIAL_LIST_CAPACITY;

  // Open the file
  words.open (filename.c_str());
    
  if (!words) {
    cerr << "Could not open " << filename << endl;
    exit(EXIT_FAILURE);
  }    
    
  // Loop to read in words
  words >> word;
  while (! words.eof()) {

    // If there isn't enough space, grow the array and copy the contents
    if (size > (capacity-1)) {

      // Create another array that is twice as large as the word_list
      string *new_word_list = new string[2 * capacity];

      // Copy the words from the word_list into the new array
      for (int index=0; (index < capacity); index++) {
        new_word_list[index] = word_list[index];
      }

      delete []word_list;
      word_list = new_word_list;

      capacity *=2;
    }

    // Save the word
    word_list[size] = word;
	size++;

    // Read in next word
    words >> word;
  }

  words.close();
}

int main (int argc, char *argv[]) {

  // An array of string objects to store our
  // word list.
  string *word_list; 
  int capacity = 0;

  // Read the word list file
  build_wordlist (word_list, capacity, "words.txt");

  // Print out the words
  for (int index=0; (index < capacity) && (word_list[index] != ""); 
       index++) {
    cout << word_list[index] << endl;
  }
  
  return EXIT_SUCCESS;  
}