利用字符出现的次数，编写一个方法，实现基本的字符串压缩功能。

利用字符出现的次数，编写一个方法，实现基本的字符串压缩功能。比如，字符串为aabccccaaa，会变为a2b1c5a3.若“压缩”后的字符串没有变短，则返回原先的字符串。

1.使用stringstream将int转化为string

2string (1)

string& append (const string& str);

substring (2)

string& append (const string& str, size_t subpos, size_t sublen);

c-string (3)

string& append (const char* s);

buffer (4)

string& append (const char* s, size_t n);

fill (5)

string& append (size_t n, char c);

range (6)

template <class InputIterator>   string& append (InputIterator first, InputIterator last);

initializer list(7)

string& append (initializer_list<char> il);

3.

std::string::push_back

void push_back (char c);

Append character to string

Appends character c to the end of the string, increasing its length by one.

string StringCompress(const string &s){string retStr;if(s.length() == 0)return retStr;char tmpChar = s.at(0);int charCount = 0;for(string::const_iterator it = s.begin();it != s.end();it++){if(*it ==tmpChar){charCount++;}else{retStr.push_back(tmpChar);//使用stringstream将int转化为stringstringstream ss;ss<<charCount;string tmpStr = ss.str();retStr.append(tmpStr);tmpChar = *it;charCount = 1;}if (it == s.end()-1){retStr.push_back(tmpChar);//使用stringstream将int转化为stringstringstream ss;ss<<charCount;string tmpStr = ss.str();retStr.append(tmpStr);}}if (retStr.length()<s.length()){return retStr;}else{return s;}}