Merge pull request #7 from jedelbo/master

Added C++ implementation of 06-candy-factory.

06-candy-factory/Makefile

@@ -0,0 +1,8 @@
+CPP_FLAGS=-std=gnu++0x
+
+tf-06: tf-06.cpp
+	$(CXX) $(CPP_FLAGS) -o $@ $<
+
+.PHONY: clean
+clean:
+	rm tf-06

06-candy-factory/tf-06.cpp

@@ -0,0 +1,180 @@
+#include <iostream>
+#include <fstream>
+#include <sstream>
+#include <regex>
+#include <map>
+
+using namespace std;
+
+struct Freq {
+  string word;
+  int freq;
+  Freq(string w, int f) : word(w), freq(f) {}
+};
+
+
+//
+// Helpers
+//
+
+static int tospace(int c)
+{
+  if (!isalpha(c))
+    return ' ';
+  else
+    return c;
+}
+
+static vector<string> get_stop_words()
+{
+  string word;
+  vector<string> stop_words;
+  ifstream is("../stop_words.txt");
+  
+  while (getline(is, word, ',')) {
+    stop_words.push_back(word);
+  }
+
+  char w[2];
+  w[1] = '\0';
+  for (char c : "abcdefghijklmopqrstuvwxyz") {
+    w[0] = c;
+    stop_words.push_back(string(w));
+  } 
+
+  sort(stop_words.begin(), stop_words.end());
+  
+  return stop_words;
+}
+
+static bool sort_by_freq(Freq x, Freq y)
+{
+  return y.freq < x.freq;
+}
+
+//
+// The functions
+//
+
+/** Takes a path to a file and returns the entire
+    contents of the file as a string
+*/
+string read_file(const char* path_to_file)
+{
+  string data;
+  ifstream is(path_to_file, std::ifstream::binary);
+
+  if (is) {
+    is.seekg (0, is.end);
+    int length = is.tellg();
+    is.seekg (0, is.beg);
+
+    char* buffer = new char [length + 1];
+    is.read(buffer,length);
+    buffer[length] = '\0';
+    data = buffer;
+    delete [] buffer;
+  }
+  return data;
+}
+
+/** Takes a string and returns a copy with all nonalphanumeric 
+    chars replaced by white space
+*/
+string filter_chars(string str_data)
+{
+  std::transform(str_data.begin(), str_data.end(), str_data.begin(), ::tospace);
+  return str_data;
+}
+
+
+/** Takes a string and returns a copy with all chars in lower case
+*/
+string normalize(string str_data)
+{
+  std::transform(str_data.begin(), str_data.end(), str_data.begin(), ::tolower);
+  return str_data;
+}    
+  
+
+/** Takes a string and scans for words, returning
+    a list of words.
+*/
+vector<string> scan(string str_data)
+{
+  string word;
+  vector<string> words;
+  istringstream is(str_data);
+  
+  while (is >> word) {
+    words.push_back(word);
+  }
+  
+  return words;
+}
+
+/** Takes a list of words and returns a copy with all stop 
+    words removed
+*/
+vector<string> remove_stop_words(vector<string> words)
+{
+  vector<string> stop_words = get_stop_words();
+  vector<string> filtered_list;
+  
+  filtered_list.reserve(words.size());
+  for (string w : words) {
+    if (!binary_search(stop_words.begin(), stop_words.end(), w))
+      filtered_list.push_back(w);
+  }
+  
+  return filtered_list;
+}
+
+/** Takes a list of words and returns a dictionary associating
+    words with frequencies of occurrence
+*/
+map<string,int> frequencies(vector<string> words)
+{
+  map<string,int> freq;
+  
+  for (string w : words) {
+    map<string,int>::iterator it = freq.find(w);
+    if (it != freq.end()) {
+      it->second++;
+    }
+    else {
+      freq.insert(pair<string,int>(w,1));
+    }
+  }
+  return freq;
+}
+
+/** Takes a dictionary of words and their frequencies
+    and returns a list of pairs where the entries are
+    sorted by frequency
+*/
+vector<Freq> sort(map<string,int> word_freq)
+{
+  vector<Freq> out_list;
+  
+  out_list.reserve(word_freq.size());
+  for (pair<string,int> p : word_freq) {
+    out_list.push_back(Freq(p.first, p.second));
+  }
+  sort(out_list.begin(), out_list.end(), sort_by_freq);
+  return out_list;
+}
+
+//
+// The main function
+//
+
+int main(int argc, char* argv[])
+{
+  vector<Freq> word_freqs = sort(frequencies(remove_stop_words(scan(normalize(filter_chars(read_file(argv[1])))))));
+  
+  for (vector<Freq>::iterator it = word_freqs.begin(); it != word_freqs.begin()+25; it++)
+    cout << it->word << " - " << it->freq << endl;
+
+  return 0;
+}