状态机学习（一）统计字符

题目来自<系统程序员成长计划>  

作者:李先静.

 

逐个字符扫描 根据是否为字母决定当前状态  由单词内状态切换到单词外 计数字符加1

 

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#include <iostream> #include <string> #include <vector>   using namespace std;   string testString = " this's a test,'Hello World!!!' Welcome to the real world, it sucks, but you are gona love it!!!";   enum STATE {     STAT_INIT,     STAT_IN_WORD,     STAT_OUT_WORD };   size_t CountWords(const string& s) {     int count = 0;     STATE state = STAT_INIT;     for (size_t i = 0; i < s.size(); i++)     {         switch (state)         {         case STAT_INIT:             if (isalpha(s[i])) {                 state = STAT_IN_WORD;             }else             {                 state = STAT_OUT_WORD;             }             break;         case STAT_IN_WORD:             if (isalpha(s[i])) {                 state = STAT_IN_WORD;             }             else {                 count++;                 state = STAT_OUT_WORD;             }             break;         case STAT_OUT_WORD:             if (isalpha(s[i])) {                 state = STAT_IN_WORD;             }             else {                 state = STAT_OUT_WORD;             }             break;         default:             break;         }//switch (state)     }     if (STAT_IN_WORD == state) {         count++;     }           return count; }   int main() {     cout << CountWords(testString) << endl;            return 0; }

　　改进版 计数以外还讲单词放入容器

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#include <iostream> #include <string> #include <vector>   using namespace std;   string testString = " this's a test,'Hello World!!!' Welcome to the real world, it sucks, but you are gona love it!!!";   enum STATE {     STAT_INIT,     STAT_IN_WORD,     STAT_OUT_WORD };   size_t CountWords(const string& s) {     int count = 0;     STATE state = STAT_INIT;     for (size_t i = 0; i < s.size(); i++)     {         switch (state)         {         case STAT_INIT:             if (isalpha(s[i])) {                 state = STAT_IN_WORD;             }else             {                 state = STAT_OUT_WORD;             }             break;         case STAT_IN_WORD:             if (isalpha(s[i])) {                 state = STAT_IN_WORD;             }             else {                 count++;                 state = STAT_OUT_WORD;             }             break;         case STAT_OUT_WORD:             if (isalpha(s[i])) {                 state = STAT_IN_WORD;             }             else {                 state = STAT_OUT_WORD;             }             break;         default:             break;         }//switch (state)     }     if (STAT_IN_WORD == state) {         count++;     }           return count; }   size_t word_segmentation(const string& s, vector<string>& strVec) {     STATE state = STAT_INIT;     size_t count = 0;     size_t subStrStart = string::npos;     size_t subStrEnd = string::npos;       for (size_t i = 0; i < s.size(); i++)     {         switch (state)         {         case STAT_INIT:             if (isalpha(s[i])) {                 subStrStart = i;                 state = STAT_IN_WORD;             }             break;         case STAT_IN_WORD:             if (!isalpha(s[i])){                 count++;                 subStrEnd = i;                 strVec.push_back(s.substr(subStrStart, subStrEnd- subStrStart));                 state = STAT_OUT_WORD;             }             break;           case STAT_OUT_WORD:             if (isalpha(s[i])) {                 subStrStart = i;                 state = STAT_IN_WORD;             }             break;         default:             break;         }//switch (state)     }           if (state == STAT_IN_WORD) {         count++;         subStrEnd = s.size();         strVec.push_back(s.substr(subStrStart, subStrEnd- subStrStart));     }       return count; }     int main() {     cout << CountWords(testString) << endl;       vector<string> strVec;     cout << word_segmentation(testString, strVec) << endl;       for (vector<string>::iterator it = strVec.begin();         it != strVec.end(); it++)     {         cout << *it << "  ";     }     cout << endl;         return 0; }

　　运行结果

19
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this s a test Hello World Welcome to the real world it sucks but y
ou are gona love it
请按任意键继续. . .