word count: initial solution.

cpp/word-count/word_count.cpp

@@ -1,12 +1,73 @@
 #include "word_count.h"
 
+#include <algorithm>
+
+
 namespace word_count {
 
 using namespace std;
 
-Words words(const string &str)
+
+Words words(const string &str, const locale &loc)
 {
-    return Words();
+    Words result;
+
+    enum {
+
+        InsideWord,
+        OutsideWord
+
+    } state(OutsideWord);
+
+
+    string::const_iterator begin, end, i;
+    i = begin = end = str.begin();
+
+    for (; i != str.end(); ++i) {
+
+        bool is_alpha_or_digit = isalpha(*i, loc) || isdigit(*i, loc);
+        bool is_word_char = is_alpha_or_digit || *i == '\'';
+
+        switch (state) {
+
+            case OutsideWord:
+
+                if (is_alpha_or_digit) {
+
+                    state = InsideWord;
+                    begin = i;
+                    end   = next(i);
+                }
+
+                break;
+
+            case InsideWord:
+
+                if (is_alpha_or_digit) {
+
+                    end = next(i);
+                }
+
+                if (!is_word_char || next(i) == str.end()) {
+
+                    state = OutsideWord;
+
+                    if (begin != end) {
+
+                        string word;
+                        word.reserve(distance(begin, end));
+                        transform(begin, end, back_inserter(word),
+                                    [=](char c){return tolower(c, loc);});
+
+                        result[word]++;
+                    }
+                }
+
+                break;
+        }
+    }
+
+    return result;
 }
 
 }